fetch_url

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

Annotations only declare readOnlyHint=true; the description adds meaningful behavioral context: truncation at ~2000 chars, the conditional behavior of the query parameter, and the caveat that without a query the top of a page is often navigation. No contradiction with annotations.

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 sentences with no wasted words: purpose is front-loaded, usage examples earn their place, and the alternative is named at the end. Ideal length for the information conveyed.

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 2-parameter read-only tool with no output schema, the description covers the return shape (title, meta description, main text), the query behavior, and the decision boundary vs web_search. An agent can correctly select and invoke the tool without further clarification.

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 description coverage is 100%, so baseline is 3. Both url and query are already documented in the schema (including optional protocol handling and what query does). The main description does not add parameter-level detail beyond the schema.

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 states a specific action ('Fetch a specific URL') with a concrete result (page title, meta description, main text content up to ~2000 chars). It explicitly scopes the tool to known URLs/domains and contrasts with web_search for open-ended queries, distinguishing it from siblings.

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 explicit when-to-use ('ANY question about a specific webpage or domain') with concrete example queries and an explicit when-not-to-use with a named alternative ('For open-ended searches without a specific URL, use web_search instead.'). The decision boundary is fully spelled out.

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