AI agents call EFetch to retrieve information from Ncbi without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
EFetch is a pure data retrieval tool that queries NCBI databases and returns existing records without side effects. It matches the Read category definition: 'retrieves or queries data; no side effects.' The tool cannot create, modify, delete, or execute operations—it only fetches and returns biomedical data in response to queries.
From the tool's definition EFetch retrieves complete records from NCBI databases (PubMed, Protein, Nucleotide, etc.) by accepting ids and optional db parameters.
Attacks that exploit this kind of access
ids为要查询项的id，db为要查询的库，如不提供db，则默认在pubmed库中查找。返回结果为所在库的完整记录。. It is categorised as a Read tool in the Ncbi MCP Server, which means it retrieves data without modifying state.
Register the Ncbi MCP server in PolicyLayer and add a rule for EFetch: 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 Ncbi. Nothing to install.
EFetch 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 EFetch 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 EFetch. 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.
EFetch is provided by the Ncbi MCP server (qigoki/ncbi-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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