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

Annotations cover the safety profile (readOnly, idempotent, openWorld), and the description adds substantive context beyond them: per-URL pricing, no charge when no URL was read, 20 s bound with typical 1-5 s latency, 422 not charged for >10 URLs, and a prompt-injection warning about returned page text. That is unusually complete behavioral disclosure.

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?

Dense and front-loaded, with every clause carrying operational information. The leading position of pricing before the purpose statement is slightly awkward for scanning, but almost no sentence is 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?

For an 11-parameter, high-complexity fetch tool with an output schema, the description covers cost, limits, latency, failure semantics, and the accepted-but-ignored parameter family. Nothing an agent needs before calling it is missing, and return values are handled by the output schema.

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 coverage is 100%, so the baseline is 3; the description still adds meaning by generalizing which inputs matter ('urls' and optional 'text'; the other options of the common contents API are accepted and ignored) and by calling out that highlights and summary are ignored. It does not add format detail for the urls items, which the schema already carries.

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 ('Get the contents of 1-10 URLs: web page to text for a list of URLs') plus the exact return shape (Markdown, 50,000 chars each). It also explicitly distinguishes itself from the sibling render_page ('For one page with JavaScript use render_page').

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 selection conditions: use render_page for a single JS page, this tool is static fetch only, no JavaScript. It also spells out limits (more than 10 URLs is a 422), pricing tiers, and the free-trial condition, so an agent knows both when to pick it and what it will cost.

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