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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description goes well beyond them: 1-hour caching with <5ms cache hits, $0.0002 per call, 5 free calls per agent_id, failed calls never charged, and the payment-required quote being a non-fatal error with retry paths (agd_pass_ key or tx_hash). This is unusually rich 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?

Front-loaded with the core purpose, then usage, then payment mechanics, with no wasted throat-clearing. It is dense and long, and the pricing detail ('first 5 calls per agent_id are free') partially repeats the earlier free-call instruction, costing it the top score.

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?

An output schema exists, so return values need not be explained; the description instead covers the auth/payment lifecycle, caching, and input alternatives. Nothing an agent needs to invoke this correctly is missing.

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, but the description adds cross-parameter interaction guidance the schema only states per-field: 'Provide either url or html (when html is supplied, url is not fetched and only labels the cache key)' and 'Omit agent_id and tx_hash during your 5 free calls'. That is genuine added value over the individual field descriptions.

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 ('Extract an ultra-compact structural outline... listing its H1-H4 headings and exact token count per section') with a clear negative scope ('without returning body prose'). It distinguishes itself cleanly from distill_webpage and extract_structured_data by naming them.

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?

Contains explicit WHEN TO USE ('first on long or unfamiliar pages to inspect structure and token cost before calling distill_webpage') and WHEN NOT TO USE sections, each naming the correct alternative and the condition that selects it. No inference is required from the agent.

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