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fetch-mcp

by YawLabs
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TypeScript
Remote

fetch_meta

Read-onlyIdempotent

Extract head metadata from a URL to preview a page: title, description, canonical, Open Graph, Twitter Card, article tags, icons, feeds, and JSON-LD, with duplicate keys in arrays.

Instructions

GET a URL and extract its head metadata: title, description, canonical, language, robots directive, Open Graph / Twitter Card / article: properties, icon links, RSS/Atom feed links, and any JSON-LD (schema.org) blocks. Keys that appear more than once (e.g. multiple og:image tags) are additionally returned via ogAll/twitterAll/articleAll arrays. Ideal for previewing a page before fully reading it.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
urlYesURL to extract metadata from
max_bytesNoDefault 2MiB — metadata lives in <head>
timeout_msNo
user_agentNo
max_redirectsNo
allow_private_hostsNo

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.6.1

TDQS

A4/5.0
Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds behavioral value by disclosing that duplicate metadata keys are rolled up into ogAll/twitterAll/articleAll arrays and that metadata lives in the <head>, beyond what annotations state.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is compact for the amount of behavior it covers: one dense sentence states the output, one explains duplicate-key handling, and one gives the usage intent. Every sentence contributes distinct information without padding.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The absence of an output schema raises the description's burden, and it does provide a strong account of the return shape, which is good. However, it remains incomplete for a 6-parameter tool because several parameters (timeout_ms, user_agent, max_redirects, allow_private_hosts) have no description-level semantics, even though their names are self-explanatory.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters2/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

With only 33% schema description coverage, the description needed to clarify the four undocumented parameters, but it only adds context for url and max_bytes (via the schema note about the 2MiB default). timeout_ms, user_agent, max_redirects, and allow_private_hosts are left to be inferred from their names, and the security-relevant allow_private_hosts gets no explanation.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description uses the specific verb 'extract' applied to a URL's head metadata and enumerates the exact fields returned (title, description, canonical, Open Graph, Twitter Card, JSON-LD, RSS/ATOM feeds), making its scope unmistakable. It also contrasts with 'fully reading' a page, which separates it from sibling fetch_reader/http_get even without naming them.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

'Ideal for previewing a page before fully reading it' gives a clear when-to-use signal and implies that full-content extraction is the alternative. It does not name sibling tools or provide an explicit when-not-to-use statement, so it falls just short of a 5.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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