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

Adds genuinely useful behavior beyond the annotations: invalid URLs degrade to per-row errors while HTTP status stays 200, result order is preserved, and each URL consumes one unit of a 60 fetches/hour budget. This is exactly the kind of cost/error context annotations cannot convey. It stops short of 5 because the shape of a successful per-URL result is never described.

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?

Four short sentences, zero filler, and the batch scope is front-loaded. Every clause (order, error handling, rate budget) carries information an agent needs.

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?

With no output schema, the description should cover return values; it does so partially by explaining per-row errors and order preservation, but never says what a successful row contains. Combined with the rate-budget disclosure, coverage is good but not complete.

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% and the single 'urls' parameter already documents 'Up to 20 http(s) URLs.' The description's 'up to 20' and 'one per URL' cost note mirror the schema's maxItems rather than adding new syntax or format meaning. Baseline 3 applies when the schema carries the load.

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+resource: 'Indexability check for up to 20 URLs in one call.' The batch scope implicitly distinguishes it from stillindexed_check_url, but the sibling is never named, so an agent must infer the relationship rather than being told it.

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?

Batch capability is stated, which implies using this instead of the single-URL checker for multiple URLs, but there is no explicit when-to-use/when-not guidance and no mention of the alternatives among the eight sibling tools (check_url, check_domain, check_robots, etc.).

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