Fetch server

Fetches URLs and converts HTML pages to markdown for the model, mirroring the reference mcp-server-fetch server.

• Identity: mcp-fetch (crate version)
• Capabilities: tools, prompts
• Invocation: modelcontextprotocol fetch or modelcontextprotocol --fetch
• Instructions published to clients: the fetch tool obeys robots.txt unless the server was started with --ignore-robots-txt; the fetch prompt fetches without checking robots.txt

Security: the fetch server can reach local and internal IP addresses; there is no SSRF protection. See Security model.

Server options

Option	Description
--ignore-robots-txt	Skip robots.txt checks for the fetch tool
--user-agent <USER_AGENT>	Custom User-Agent for all requests, replacing both defaults
--proxy-url <URL>	Route all requests through this HTTP(S) proxy

Default user agents (unless overridden):

ModelContextProtocol/1.0 (Autonomous; +https://github.com/modelcontextprotocol/servers)
ModelContextProtocol/1.0 (User-Specified; +https://github.com/modelcontextprotocol/servers)

The autonomous agent is used by the fetch tool; the user-specified agent by the fetch prompt.

Tool: fetch

Fetches a URL and optionally extracts its contents as markdown. The tool description tells the model that it grants internet access.

Parameter	Required	Default	Bounds / notes
url	yes	—	http or https only; any other scheme is an error
max_length	no	5000	integer, 1..999999; out of range is an error
start_index	no	0	integer, ≥ 0; out of range is an error
raw	no	false	true returns the page content without HTML→markdown simplification

Web search with DuckDuckGo Lite

Use DuckDuckGo's lightweight HTML endpoint as the url when you need search results:

https://lite.duckduckgo.com/lite/?q={query}&kl={kl}&kp={kp}

• q is the URL-encoded search query.
• kl selects the region and language, such as us-en.
• kp controls Safe Search: 1 = on, -1 = moderate, -2 = off.

For example, this searches for mcp in US English with Safe Search off:

https://lite.duckduckgo.com/lite/?q=mcp&kl=us-en&kp=-2

Behavior:

• HTML → markdown by default: pages that look like HTML (first 100 characters contain <html, or text/html content type, or empty content type) are simplified unless raw: true. style, script, noscript, and template content is suppressed, never leaked. If nothing extractable remains, the result is <error>Page failed to be simplified from HTML</error>.
• Non-HTML content (JSON, plain text, ...) is returned raw with a status prefix ("Content type ... cannot be simplified to markdown, but here is the raw content:").
• Truncation is character-based: start_index resumes a previous fetch; when content is cut off, a continuation hint is appended — <error>Content truncated. Call the fetch tool with a start_index of N to get more content.</error> — and start_index beyond the end returns <error>No more content available.</error>.
• HTTP status ≥ 400 surfaces as a tool error ("Failed to fetch ... - status code 404").
• robots.txt is consulted before fetching (unless --ignore-robots-txt): unreachable → blocked; 401/403 → blocked; other 4xx → allowed; a disallow rule matching the autonomous user agent → blocked with guidance to try the fetch prompt.
• Every request has a 30-second timeout.

Prompt: fetch

A user-initiated fetch: takes url, fetches the page (no robots.txt check), and returns the content as a user prompt message with a description ("Contents of {url}"). A blank URL is rejected (invalid_params); fetch failures become a prompt message describing the failure rather than a protocol error.

Request internals

• HTTP client: reqwest with the ring rustls backend (installed explicitly at startup), charset decoding enabled.
• No redirect restrictions, no size cap on the response body itself (the tool truncates the returned text, not the download).