willow_web_fetch

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

The description discloses specific behavioral traits: it 'blocks private, loopback and other non-public destinations' with name resolution, re-checks every redirect hop (not just the first), and returns the redirect chain in `redirects`. It also notes the 'sandwich defense' when wrap=True and the required permissions. These go well beyond the annotations (readOnly, openWorld, non-destructive), which are minimal, and provide valuable operational context.

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 dense but every sentence conveys important information: purpose, alternative, security behavior, redirect handling, discovery advice, and requirements. It is front-loaded with the main action and contains no filler.

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?

The description covers the main purpose, security restrictions, redirect behavior, required permissions, and a hint about return content (text with sandwich defense, redirects). It does not explain error handling or behavior when max_bytes is exceeded, but given the lack of an output schema, the description is fairly complete. A small gap remains regarding app_id and max_bytes semantics.

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 0%, so the description must explain all parameters. It explains `wrap` (sandwich defense) and implies `url` ('Fetch a URL'), but it does not explain `app_id` or `max_bytes`. Given zero schema coverage, the description fails to compensate for two of the four parameters, leaving the agent to guess their purpose.

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 verb 'Fetch' and the resource 'URL', and explicitly distinguishes it from 'native WebFetch' and from 'willow_web_search' (which is for discovering URLs). This gives an agent a precise understanding of what the tool does and how it differs from closely related tools.

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 explicitly says 'Use willow_web_search to discover URLs first', providing a direct when-to-use instruction. It also states 'not native WebFetch', pointing to an alternative. This is clear guidance on when to call this tool versus alternatives.

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