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

Annotations already declare readOnlyHint/idempotentHint and that nothing is destructive, so 'Behavior: read-only' repeats structured data. The genuinely additive piece is the payment/auth note ('x402 or SANITY_API_KEY like the other Sanity calls'), which tells the agent a payment path may be required — but the description never says what the retrieved check looks like or whether results expire.

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?

Purpose is front-loaded and the total length is small. There is some waste: the usage sentence largely restates the purpose sentence, and the 'Behavior: read-only.' line duplicates the annotation rather than earning its place.

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 simple single-param read tool with no output schema, the description covers purpose, alternative, and auth. However, it gives no hint of the returned record's structure or how it differs from just re-running sanity_check, leaving the agent to guess what it will get back.

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 schema already says check_id comes from an earlier sanity_check result; the description restates the same provenance. With one fully documented parameter and no extra format details (e.g., id shape, whether batch ids work), baseline 3 is right.

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 — fetch a previously run check by check_id — and names the sibling tools that produce that id (sanity_check / sanity_check_batch). It is distinguishable from the sibling checks, though the bracketed '[Wicked Sanity]' prefix adds noise rather than precision.

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?

Explicitly says when to use ('re-read an earlier check by its check_id') and when not ('Not for running a new check'), which routes the agent away from sanity_check. No further exclusions or sequencing guidance are given, so it falls short of a 5.

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