Navigate to the actual TypeScript source instead of .d.ts declaration files. Useful when working with libraries that have source maps or when you want to see the implementation rather than just the type declarations.
AI agents call findSourceDefinition to retrieve information from Ts without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
Even though findSourceDefinition only reads data, uncontrolled read access leaks sensitive information and racks up API costs — an agent caught in a retry loop can make thousands of calls a minute without anyone noticing.
Attacks that exploit this kind of access
Navigate to the actual TypeScript source instead of .d.ts declaration files. Useful when working with libraries that have source maps or when you want to see the implementation rather than just the type declarations. It is categorised as a Read tool in the Ts MCP Server, which means it retrieves data without modifying state.
Register the Ts MCP server in PolicyLayer and add a rule for findSourceDefinition: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Ts. Nothing to install.
findSourceDefinition is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the findSourceDefinition rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for findSourceDefinition. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
findSourceDefinition is provided by the Ts MCP server (ts-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.