fetch_url

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

With no annotations provided, the description carries the full burden. It explicitly discloses behavioral traits: 'strip boilerplate', returns markdown, and the proxy routing for international vs. CN hosts. This goes beyond minimal operational details, though it doesn't address error handling or auth requirements.

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 two sentences, front-loaded with the primary action, followed by a relevant network routing detail. Every sentence adds necessary context with no redundant or filler content.

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 tool with two parameters and no output schema, the description sufficiently covers the return value ('markdown') and key behavior (boilerplate stripping, proxy routing). It lacks mention of error handling or non-HTML content, but these are not critical given the tool's simplicity.

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 a baseline of 3 applies. The description adds little beyond the schema; 'Fetch a URL' paraphrases the url parameter, and max_chars is already described as 'Max chars of markdown to return.' No additional parameter semantics are provided.

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 a specific verb ('Fetch'), a specific resource ('a URL'), and the output format ('return the page content as markdown'). This clearly distinguishes it from sibling tools 'web_search' and 'deep_research', which are for searching/researching rather than fetching a known URL.

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?

The description implies usage when the agent has a specific URL to retrieve, but it does not explicitly contrast with alternatives like web_search or deep_research. It lacks an explicit 'when to use' or 'when not to use' statement.

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