fetch_url_metadata

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

With no annotations, the description carries the full disclosure burden; it usefully signals this is a lightweight network call whose payload omits page body content. It says nothing about failure modes (non-HTML pages, unreachable URLs, timeouts), truncation, or whether results are cached, which matters for a network-dependent tool.

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?

Three short sentences, front-loaded with the capability, then scope, then the alternative. No filler and nothing redundant.

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 one-parameter read tool with no output schema, the description usefully enumerates the returned fields and warns about the missing page body. Only network-failure behavior is left uncovered, which is a minor gap at this complexity.

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?

Only one parameter, and schema description coverage is 0%, so the description must compensate. It implies a URL to fetch but adds no format guidance (absolute vs. relative, scheme requirements) or what happens with redirects, so meaning beyond the bare schema field is minimal.

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?

States a specific verb and resource ("fetch a URL") plus the exact outputs (title, site name, description), and explicitly bounds the scope with "does not return full page content." That is enough for an agent to distinguish it from content-extraction siblings without opening the schema.

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?

Gives an explicit use case ("for bookmark saves") and an explicit when-not with a named alternative ("use the article type instead"). The only weakness is that "the article type" does not map to any sibling tool name, so the agent must guess which tool actually performs full extraction.

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