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

Annotations only declare a generic non-readonly, non-destructive profile (openWorldHint=false, idempotentHint=false), which is thin for an async paid batch job. The description adds the crucial behavior: a report_id/report_url is returned immediately while scanning happens in the background (~10s per page), the deliverable contents, three free re-scans in 30 days, and the exact payment rails (x402/USDC on Base or credit token).

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 action and delivery model, and nearly every sentence carries distinct information (async timing, report contents, read-back tool, alternative tool, pricing). Minor redundancy between the title's '$69' and the trailing 'Costs $69.00' sentence keeps it from a 5.

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 paid, async, multi-url tool the description covers delivery semantics, cost, payment paths, follow-up tools, and alternatives. An output schema exists, so it correctly does not need to enumerate return fields.

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 both parameters (urls, credit_token) are already documented in the schema, including the 1-20/3-hostname limit. The description adds only a general mention of credit-token payment, which the schema already covers in more detail; baseline 3 applies.

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 ('Order a full reachability report for one site') plus concrete scope ('up to 20 pages, each checked from nine common clients'). It also explicitly contrasts itself with the sibling tools reach and reach_report_status, so an agent can route without opening a schema.

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?

Explicit when-to-use routing: 'Use reach_report_status to read it' and 'For a single quick check use the reach tool instead.' It even handles the no-payment prerequisite by naming credits_trial for free credit, which removes the most likely invocation failure.

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