fetch_metadata

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

States it has no side effects and returns an error if the URL is unreachable. However, does not detail behavior regarding redirects, timeouts, or authentication, though given the tool's simplicity, the disclosed traits are sufficient.

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

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

The description is well-structured and front-loaded, listing extracted metadata clearly. It is concise but could be slightly shorter; still effective.

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

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

For a simple single-parameter tool with no output schema, the description fully covers input, output shape (structured JSON with omitted missing fields), error conditions, and usage context.

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

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

Schema coverage is 100% with a clear parameter description. The tool description adds no additional meaning beyond what the schema provides, so baseline score applies.

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

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

The description clearly states the tool fetches a URL and extracts metadata including title, meta description, Open Graph tags, etc. It explicitly distinguishes from siblings by warning not to use for body text and recommending fetch_extract or html_to_markdown instead.

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

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

Provides explicit when-to-use guidance ('ideal for link previews, SEO audits, and content classification') and when-not-to-use with alternatives ('Do NOT use to extract page body text — use fetch_extract or html_to_markdown instead').

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