Fetches JSON content from a URL
AI agents call fetch_json to retrieve information from Fetch MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves and converts existing web content into JSON format. It queries data from a URL without modifying, deleting, executing code, or performing financial transactions. This is a straightforward Read operation with minimal security risk unless the fetched data itself is misused downstream.
From the tool's definition Tool name 'fetch_json' and description 'Fetches JSON content from a URL' indicate retrieval of data with no side effects. The server description emphasizes 'web data retrieval and transformation' as read-only operations.
Attacks that exploit this kind of access
Fetches JSON content from a URL. It is categorised as a Read tool in the Fetch MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Fetch MCP Server MCP server in PolicyLayer and add a rule for fetch_json: 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 Fetch MCP Server. Nothing to install.
fetch_json 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 fetch_json 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 fetch_json. 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.
fetch_json is provided by the Fetch MCP Server MCP server (solonabot/fetch-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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