What can @sigilcore/mcp-proxy do?

mcp tool wrapping with sigil intent attestations, mcp proxy middleware with attestation interception, sigil intent attestation validation and enforcement, agent identity and intent binding in tool calls, policy-based tool access control with attestation validation, audit logging and compliance tracking for tool invocations

@sigilcore/mcp-proxy

MCP ServerFree

Wraps MCP tool connections in Sigil Intent Attestations

Open Source

/ 100

6 capabilities

Capabilities6 decomposed

mcp tool wrapping with sigil intent attestations

Medium confidence

Intercepts MCP (Model Context Protocol) tool invocations and wraps them in Sigil Intent Attestations, a cryptographic attestation layer that verifies the intent and authorization of tool calls before execution. This works by hooking into the MCP tool registry, capturing tool call metadata (name, arguments, context), generating attestation signatures, and validating them against a Sigil policy engine before delegating to the underlying tool implementation.

Solves for

I want to ensure that only authorized LLM agents can invoke specific tools in my MCP serverI need cryptographic proof that a tool was called with the correct intent, not maliciously or out-of-contextI want to audit and track which agents called which tools and with what parametersI need to prevent prompt injection attacks that trick an LLM into calling tools it shouldn't

Best for

teams building multi-agent systems with shared MCP tool servers

enterprises requiring compliance and audit trails for LLM-driven tool access

developers protecting sensitive tools (database writes, API calls, file operations) from unauthorized LLM invocation

Requires

Node.js 16+ (MCP server runtime)

Active Sigil Intent Attestation service or self-hosted Sigil validator

MCP server implementation (e.g., via @modelcontextprotocol/sdk)

Limitations

Adds cryptographic overhead (~5-50ms per tool call depending on attestation complexity) that may impact latency-sensitive workflows

Requires pre-established trust relationship and key exchange with Sigil infrastructure — not suitable for ad-hoc tool sharing

Attestation validation is only as strong as the Sigil policy engine; misconfigured policies can create false sense of security

What makes it unique

Implements attestation-based tool access control at the MCP protocol layer using Sigil Intent Attestations, a cryptographic framework that binds tool invocations to agent identity and intent — rather than relying on coarse-grained API keys or role-based access control, it validates the semantic intent of each tool call

vs alternatives

Provides finer-grained security than standard MCP server authentication (which typically uses API keys) by cryptographically verifying agent intent for each tool call, preventing prompt injection and unauthorized tool use even if an agent has general MCP access

mcp proxy middleware with attestation interception

Medium confidence

Acts as a transparent proxy layer between MCP clients (LLM agents, applications) and MCP tool servers, intercepting all tool calls at the protocol level and injecting attestation validation logic without requiring changes to the underlying tool implementations. The proxy parses incoming MCP messages, extracts tool call metadata, validates attestations against Sigil policies, and either forwards the call to the tool server or rejects it with detailed error information.

Solves for

I want to add security to existing MCP tool servers without modifying their codeI need a centralized point to enforce tool access policies across multiple MCP serversI want to transparently log and audit all tool invocations passing through my infrastructureI need to rate-limit or throttle tool calls based on agent identity or tool type

Best for

platform teams operating shared MCP infrastructure for multiple internal agents

security-conscious organizations retrofitting authorization to existing MCP deployments

developers building multi-tenant LLM applications where tool access must be isolated per tenant

Requires

Node.js 16+ runtime for the proxy process

MCP client SDK (e.g., @modelcontextprotocol/sdk) to communicate with tool servers

Sigil Intent Attestation infrastructure or validator service

Limitations

Proxy adds network hop and processing latency (~10-100ms per tool call) compared to direct tool access

Requires careful configuration of attestation policies to avoid false rejections that break legitimate workflows

Stateless proxy design means no built-in session management or connection pooling — high-concurrency scenarios may require load balancing

What makes it unique

Implements MCP as a transparent proxy middleware that validates attestations at the protocol level without requiring tool server modifications, using a stateless architecture that can be deployed as a sidecar or centralized service in front of multiple MCP servers

vs alternatives

Simpler to deploy than modifying each tool server individually, and more flexible than embedding attestation logic directly in tools since policies can be updated without redeploying tool code

sigil intent attestation validation and enforcement

Medium confidence

Validates cryptographic Sigil Intent Attestations embedded in or accompanying MCP tool calls, verifying that the attestation signature is valid, the agent identity matches the policy, and the tool/argument combination is authorized. This involves signature verification using public keys, policy lookup and evaluation, timestamp validation to prevent replay attacks, and detailed error reporting if validation fails.

Solves for

I want to verify that a tool call came from an authorized agent and wasn't forged or modified in transitI need to enforce fine-grained policies like 'only Agent A can call database_write with table=users'I want to detect and reject replay attacks where an old, valid attestation is reusedI need detailed audit information about why a tool call was rejected

Best for

high-security environments where tool access must be cryptographically verified

regulated industries (finance, healthcare) requiring non-repudiation and audit trails

multi-agent systems where agent identity and intent must be cryptographically bound to tool calls

Requires

Sigil Intent Attestation service or self-hosted validator with public key infrastructure

Cryptographic libraries for signature verification (e.g., Node.js crypto module with RSA/ECDSA support)

Policy engine or configuration system to define and lookup attestation policies

Limitations

Attestation validation requires access to Sigil public keys and policy definitions, adding external dependency

Clock skew between client and validator can cause timestamp validation failures; requires NTP synchronization

Revocation of compromised agent keys requires policy updates; no real-time revocation mechanism without external service

What makes it unique

Implements cryptographic attestation validation using Sigil Intent Attestations, which bind agent identity, tool intent, and authorization in a single cryptographic token — rather than relying on separate authentication and authorization layers, it validates intent and authorization together

vs alternatives

More robust than API key-based authorization because attestations are cryptographically signed and include agent identity and intent, making them resistant to key theft and enabling fine-grained policy enforcement without requiring a separate authorization service

agent identity and intent binding in tool calls

Medium confidence

Captures and binds agent identity (who is calling the tool) and intent (what the agent intends to accomplish) into Sigil attestations that accompany each MCP tool call. This works by extracting agent metadata from the MCP context, generating a cryptographic commitment to the tool call parameters and intent, signing it with the agent's key, and embedding the attestation in the MCP message so the tool server can verify it.

Solves for

I want to know which agent called a tool and prove it cryptographicallyI need to bind the agent's stated intent to the tool call so I can audit what the agent was trying to doI want to prevent an agent from claiming it didn't make a tool call (non-repudiation)I need to enforce policies based on agent identity and intent, not just tool name

Best for

multi-agent systems where agent accountability and non-repudiation are critical

compliance-heavy environments requiring detailed audit trails of agent actions

systems where tool access policies depend on agent identity and stated intent

Requires

Agent identity system (e.g., agent registry with unique IDs and associated public keys)

Cryptographic key material for each agent (private key for signing attestations)

MCP context that includes agent metadata (ID, name, intent description)

Limitations

Requires agent key material to be available at call time; key management complexity increases with number of agents

Intent binding is only as accurate as the agent's self-reported intent; malicious agents can misrepresent intent

Attestation generation adds latency (~5-20ms per call) due to cryptographic signing

What makes it unique

Binds agent identity and intent into cryptographic attestations at the MCP protocol level, creating a non-repudiation mechanism where agents cannot deny making tool calls and intent is cryptographically committed before execution

vs alternatives

Stronger accountability than logging-based approaches because attestations are cryptographically signed by the agent, making them tamper-proof and suitable for compliance audits; more fine-grained than role-based access control because it includes agent intent

policy-based tool access control with attestation validation

Medium confidence

Evaluates Sigil attestations against a policy engine that defines which agents can call which tools with which parameters. The policy engine looks up policies by agent ID and tool name, checks if the attestation matches the policy requirements (e.g., specific argument values, time-based restrictions), and either allows or denies the tool call. Policies are typically defined in a declarative format (JSON, YAML) and can include conditions like 'only Agent A can call database_write', 'Agent B can only call read_only tools', or 'this tool can only be called between 9am-5pm'.

Solves for

I want to define fine-grained policies for which agents can call which toolsI need to enforce parameter-level restrictions (e.g., 'Agent A can only write to table X')I want to enforce time-based or context-based restrictions on tool accessI need to update policies without redeploying agents or tool servers

Best for

organizations with complex tool access requirements and multiple agents

teams that need to update tool access policies frequently without code changes

systems where tool access must be restricted based on agent identity, parameters, or context

Requires

Policy definition system (JSON, YAML, or custom DSL)

Policy storage and retrieval (file system, database, or configuration service)

Policy evaluation engine (custom logic or rules engine like OPA, Rego)

Limitations

Policy evaluation adds latency (~5-50ms per tool call) depending on policy complexity

Policies must be manually maintained and kept in sync with actual tool capabilities; no automatic validation

No built-in support for dynamic policies that change based on runtime conditions (e.g., agent reputation scores)

What makes it unique

Implements policy-based access control at the MCP protocol level using Sigil attestations as the authorization token, allowing fine-grained policies to be defined and updated independently of tool server code

vs alternatives

More flexible than hardcoded authorization checks in tool servers because policies are externalized and can be updated without redeploying; more expressive than simple role-based access control because policies can include parameter-level restrictions and context-based conditions

audit logging and compliance tracking for tool invocations

Medium confidence

Automatically logs all tool invocations that pass through the MCP proxy, capturing agent identity, tool name, arguments, attestation status, policy evaluation result, timestamp, and execution result. Logs are structured (JSON format) and include enough detail for compliance audits, forensic analysis, and debugging. The logging system can be configured to write to files, databases, or external logging services.

Solves for

I need to audit which agents called which tools and when, for compliance purposesI want to investigate security incidents by reviewing tool call historyI need to track tool usage patterns to understand agent behaviorI want to generate compliance reports showing that tool access was properly authorized

Best for

regulated industries (finance, healthcare, government) requiring detailed audit trails

security teams investigating incidents or suspicious agent behavior

compliance officers generating audit reports for external auditors

Requires

Logging library (e.g., Winston, Bunyan, or custom JSON logger)

Log storage backend (file system, database, or external service like ELK, Datadog, Splunk)

Log retention and rotation policies

Limitations

Logging adds I/O overhead (~10-100ms per tool call depending on logging backend) that can impact throughput

Logs can grow very large in high-volume systems, requiring log rotation and archival strategies

Sensitive data in tool arguments may be logged, requiring careful log access control and data retention policies

What makes it unique

Provides automatic, structured audit logging at the MCP protocol level with cryptographic attestation validation results, enabling compliance-grade audit trails without requiring changes to tool servers or agents

vs alternatives

More comprehensive than tool-level logging because it captures all tool invocations in a centralized location with consistent formatting; more trustworthy than agent-side logging because the proxy is outside the agent's control

Capabilities are decomposed by AI analysis. Each maps to specific user intents and improves with match feedback.

Related Artifactssharing capabilities

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mcp-runtime-guard

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callmux

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mcp server proxying with protocol translation

1 shared capability

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@aiclude/mcp-guard

MCP runtime security proxy — intercepts and enforces security policies on MCP tool calls

mcp tool call interception and policy enforcement

1 shared capability

Best For

✓teams building multi-agent systems with shared MCP tool servers
✓enterprises requiring compliance and audit trails for LLM-driven tool access
✓developers protecting sensitive tools (database writes, API calls, file operations) from unauthorized LLM invocation
✓platform teams operating shared MCP infrastructure for multiple internal agents
✓security-conscious organizations retrofitting authorization to existing MCP deployments
✓developers building multi-tenant LLM applications where tool access must be isolated per tenant
✓high-security environments where tool access must be cryptographically verified
✓regulated industries (finance, healthcare) requiring non-repudiation and audit trails

Known Limitations

⚠Adds cryptographic overhead (~5-50ms per tool call depending on attestation complexity) that may impact latency-sensitive workflows
⚠Requires pre-established trust relationship and key exchange with Sigil infrastructure — not suitable for ad-hoc tool sharing
⚠Attestation validation is only as strong as the Sigil policy engine; misconfigured policies can create false sense of security
⚠No built-in support for revocation or key rotation — requires manual policy updates to block compromised agents
⚠Proxy adds network hop and processing latency (~10-100ms per tool call) compared to direct tool access
⚠Requires careful configuration of attestation policies to avoid false rejections that break legitimate workflows

Requirements

Node.js 16+ (MCP server runtime)Active Sigil Intent Attestation service or self-hosted Sigil validatorMCP server implementation (e.g., via @modelcontextprotocol/sdk)Cryptographic key material for signing/verifying attestationsNode.js 16+ runtime for the proxy processMCP client SDK (e.g., @modelcontextprotocol/sdk) to communicate with tool serversSigil Intent Attestation infrastructure or validator serviceNetwork connectivity between proxy and both MCP clients and tool servers

Input / Output

Accepts: MCP tool call objects (name, arguments, context metadata), Sigil attestation tokens (JWT-like structures with cryptographic signatures), Policy definitions (JSON or similar format specifying allowed tool/agent pairs), MCP protocol messages (JSON-RPC format with tool call requests), Sigil attestation tokens embedded in MCP message headers or metadata, Policy configuration (YAML, JSON, or environment variables), Sigil attestation tokens (cryptographically signed JWT-like structures), MCP tool call metadata (tool name, arguments, context), Policy definitions (mapping agent IDs and tool names to allowed operations), Agent metadata (ID, name, public key), Tool call parameters (tool name, arguments), Intent description (natural language or structured format describing what the agent is trying to do), Sigil attestation (containing agent ID, tool name, arguments), Policy definitions (declarative rules mapping agents to allowed tools and parameters), Tool call metadata (tool name, arguments, context), Tool invocation metadata (agent ID, tool name, arguments, timestamp), Attestation validation result (valid/invalid, reason), Policy evaluation result (allow/deny, policy matched), Tool execution result (success/failure, return value)

Produces: Validated tool execution results (pass-through if attestation succeeds), Attestation validation errors (with detailed reason for rejection), Audit logs (tool call, agent identity, timestamp, attestation status), MCP protocol responses (tool results or error messages), Attestation validation logs (structured JSON with call metadata, validation result, timestamp), Rejection responses with reason codes (e.g., 'ATTESTATION_INVALID', 'POLICY_DENIED'), Validation result (boolean: valid/invalid), Detailed validation error (e.g., 'SIGNATURE_INVALID', 'POLICY_DENIED', 'TIMESTAMP_EXPIRED'), Audit log entry with validation details (agent ID, tool name, timestamp, policy matched), Sigil attestation token (cryptographically signed structure binding agent, intent, and tool call), Attestation metadata (agent ID, timestamp, intent hash, signature), Policy evaluation result (allow/deny), Detailed denial reason (e.g., 'AGENT_NOT_AUTHORIZED', 'PARAMETER_RESTRICTED', 'TIME_RESTRICTED'), Audit log entry with policy matched and evaluation details, Structured audit log entries (JSON format with all relevant metadata), Compliance reports (summaries of tool access by agent, tool, or time period), Forensic analysis data (detailed logs for specific agents or tools)

UnfragileRank

Adoption5%(25% weight)

Quality12%(25% weight)

Ecosystem30%(15% weight)

Match Graph25%(30% weight)

Freshness75%(5% weight)

UnfragileRank is computed from adoption signals, documentation quality, ecosystem connectivity, match graph feedback, and freshness. No artifact can pay for a higher rank.

Type: MCP Server

6 capabilities

Visit @sigilcore/mcp-proxy→

Package Details

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Registry

0.1.0

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Wraps MCP tool connections in Sigil Intent Attestations

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Capabilities6 decomposed

mcp tool wrapping with sigil intent attestations

Medium confidence

Solves for

Best for

teams building multi-agent systems with shared MCP tool servers

enterprises requiring compliance and audit trails for LLM-driven tool access

developers protecting sensitive tools (database writes, API calls, file operations) from unauthorized LLM invocation

Requires

Node.js 16+ (MCP server runtime)

Active Sigil Intent Attestation service or self-hosted Sigil validator

MCP server implementation (e.g., via @modelcontextprotocol/sdk)

Limitations

Adds cryptographic overhead (~5-50ms per tool call depending on attestation complexity) that may impact latency-sensitive workflows

Requires pre-established trust relationship and key exchange with Sigil infrastructure — not suitable for ad-hoc tool sharing

Attestation validation is only as strong as the Sigil policy engine; misconfigured policies can create false sense of security

What makes it unique

vs alternatives

mcp proxy middleware with attestation interception

Medium confidence

Solves for

Best for

platform teams operating shared MCP infrastructure for multiple internal agents

security-conscious organizations retrofitting authorization to existing MCP deployments

developers building multi-tenant LLM applications where tool access must be isolated per tenant

Requires

Node.js 16+ runtime for the proxy process

MCP client SDK (e.g., @modelcontextprotocol/sdk) to communicate with tool servers

Sigil Intent Attestation infrastructure or validator service

Limitations

Proxy adds network hop and processing latency (~10-100ms per tool call) compared to direct tool access

Requires careful configuration of attestation policies to avoid false rejections that break legitimate workflows

Stateless proxy design means no built-in session management or connection pooling — high-concurrency scenarios may require load balancing

What makes it unique

vs alternatives

Simpler to deploy than modifying each tool server individually, and more flexible than embedding attestation logic directly in tools since policies can be updated without redeploying tool code

sigil intent attestation validation and enforcement

Medium confidence

Solves for

Best for

high-security environments where tool access must be cryptographically verified

regulated industries (finance, healthcare) requiring non-repudiation and audit trails

multi-agent systems where agent identity and intent must be cryptographically bound to tool calls

Requires

Sigil Intent Attestation service or self-hosted validator with public key infrastructure

Cryptographic libraries for signature verification (e.g., Node.js crypto module with RSA/ECDSA support)

Policy engine or configuration system to define and lookup attestation policies

Limitations

Attestation validation requires access to Sigil public keys and policy definitions, adding external dependency

Clock skew between client and validator can cause timestamp validation failures; requires NTP synchronization

Revocation of compromised agent keys requires policy updates; no real-time revocation mechanism without external service

What makes it unique

vs alternatives

agent identity and intent binding in tool calls

Medium confidence

Solves for

Best for

multi-agent systems where agent accountability and non-repudiation are critical

compliance-heavy environments requiring detailed audit trails of agent actions

systems where tool access policies depend on agent identity and stated intent

Requires

Agent identity system (e.g., agent registry with unique IDs and associated public keys)

Cryptographic key material for each agent (private key for signing attestations)

MCP context that includes agent metadata (ID, name, intent description)

Limitations

Requires agent key material to be available at call time; key management complexity increases with number of agents

Intent binding is only as accurate as the agent's self-reported intent; malicious agents can misrepresent intent

Attestation generation adds latency (~5-20ms per call) due to cryptographic signing

What makes it unique

vs alternatives

policy-based tool access control with attestation validation

Medium confidence

Solves for

Best for

organizations with complex tool access requirements and multiple agents

teams that need to update tool access policies frequently without code changes

systems where tool access must be restricted based on agent identity, parameters, or context

Requires

Policy definition system (JSON, YAML, or custom DSL)

Policy storage and retrieval (file system, database, or configuration service)

Policy evaluation engine (custom logic or rules engine like OPA, Rego)

Limitations

Policy evaluation adds latency (~5-50ms per tool call) depending on policy complexity

Policies must be manually maintained and kept in sync with actual tool capabilities; no automatic validation

No built-in support for dynamic policies that change based on runtime conditions (e.g., agent reputation scores)

What makes it unique

vs alternatives

audit logging and compliance tracking for tool invocations

Medium confidence

Solves for

Best for

regulated industries (finance, healthcare, government) requiring detailed audit trails

security teams investigating incidents or suspicious agent behavior

compliance officers generating audit reports for external auditors

Requires

Logging library (e.g., Winston, Bunyan, or custom JSON logger)

Log storage backend (file system, database, or external service like ELK, Datadog, Splunk)

Log retention and rotation policies

Limitations

Logging adds I/O overhead (~10-100ms per tool call depending on logging backend) that can impact throughput

Logs can grow very large in high-volume systems, requiring log rotation and archival strategies

Sensitive data in tool arguments may be logged, requiring careful log access control and data retention policies

What makes it unique

vs alternatives

Capabilities are decomposed by AI analysis. Each maps to specific user intents and improves with match feedback.

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@sigilcore/mcp-proxy

Capabilities6 decomposed

mcp tool wrapping with sigil intent attestations

mcp proxy middleware with attestation interception

sigil intent attestation validation and enforcement

agent identity and intent binding in tool calls

policy-based tool access control with attestation validation

audit logging and compliance tracking for tool invocations

Related Artifactssharing capabilities

@treeship/mcp

@policylayer/intercept

mcp-runtime-guard

tegata

callmux

@aiclude/mcp-guard

Best For

Known Limitations

Requirements

Input / Output

UnfragileRank

Package Details

About

Categories

Alternatives to @sigilcore/mcp-proxy

Are you the builder of @sigilcore/mcp-proxy?

Get the weekly brief

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@sigilcore/mcp-proxy

Capabilities6 decomposed

mcp tool wrapping with sigil intent attestations

mcp proxy middleware with attestation interception

sigil intent attestation validation and enforcement

agent identity and intent binding in tool calls

policy-based tool access control with attestation validation

audit logging and compliance tracking for tool invocations

Related Artifactssharing capabilities

@treeship/mcp

@policylayer/intercept

mcp-runtime-guard

tegata

callmux

@aiclude/mcp-guard

Best For

Known Limitations

Requirements

Input / Output

UnfragileRank

Package Details

About

Categories

Alternatives to @sigilcore/mcp-proxy

Are you the builder of @sigilcore/mcp-proxy?

Get the weekly brief

Data Sources