Fetch rich results using the callback_key from web_search
AI agents call rich_fetch to retrieve information from Search MCP without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves pre-computed search result data using a callback key from a prior web search. It has no side effects, does not modify data, does not execute code or commands, and does not delete or move resources. It is purely a read operation that queries and returns search results.
From the tool's definition Tool description: 'Fetch rich results using the callback_key from web_search' — the word 'fetch' indicates data retrieval.
Attacks that exploit this kind of access
Fetch rich results using the callback_key from web_search. It is categorised as a Read tool in the Search MCP MCP Server, which means it retrieves data without modifying state.
Register the Search MCP server in PolicyLayer and add a rule for rich_fetch: 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 Search MCP. Nothing to install.
rich_fetch 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 rich_fetch 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 rich_fetch. 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.
rich_fetch is provided by the Search MCP server (nanameru/websearch-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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