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

With no annotations provided, the description carries full behavioral burden and does well: it discloses cache reuse, output fields (sha256 hash and fetched_at), the public-URL restriction, and the funded API key requirement. These are meaningful behavioral traits beyond a bare 'fetch page' statement.

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, each earning its place: what it returns, how caching works, and the key requirement. The most important information is front-loaded, with 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?

Despite no output schema, the description names the return contents (readable text, sha256 hash, fetched_at), covers both parameters through schema plus description, and gives the auth prerequisite. This is complete enough for an agent to select and invoke the tool correctly.

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 the schema already explains url and max_age_s. The description reinforces the caching semantics by saying 'Reuses a stored copy if it is newer than max_age_s,' but it does not add substantial new meaning beyond what the schema already provides.

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 verb and resource: 'Return readable text for a public http(s) URL.' It also clarifies caching behavior and output contents, which distinguishes it from the sibling search_pages by making clear this tool fetches a single URL rather than searching.

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 gives clear context for use: it applies to public http(s) URLs, can reuse cached snapshots based on max_age_s, and requires a funded API key. It does not explicitly mention when not to use it or compare it to search_pages, so it stops short of full alternative guidance.

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