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

Annotations already cover the safety profile (readOnlyHint, destructiveHint=false), yet the description adds substantial behavioral detail the agent could not infer: the key is masked to its last four characters, only keyFileUrl carries the full key while unverified, both conditions are required for engines to accept submissions, and keyFileVerified=null means an inconclusive check (timeout/bot rule), not a failure.

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?

A single dense paragraph that is well front-loaded: the trigger and the two reported facts come first, semantics of each field follow, and the sibling routing lands last. Almost every sentence earns its place, though the return-field detail is packed tightly enough to be slightly heavy for one run-on block.

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?

Despite an output schema existing (so return values need not be spelled out), the description goes further and explains the meaning of keyFileUrl and the null case of keyFileVerified. It also covers the remediation path (update_indexnow_settings with generateKey: true) needed to act on the result. Nothing an agent needs 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?

There is a single siteUrl parameter with 0% schema description coverage, so the description carries the compensation burden. It refers to 'a site' and ties the whole check to it, implying the parameter's role, but never states the expected format of siteUrl (host vs full URL). Partial compensation only.

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 (retrieve IndexNow settings) and immediately scopes it: it reports both whether an API key is configured and whether the key file is reachable. This clearly separates it from list_indexnow_submissions (past submissions) and submit_indexnow_urls (submission action), which are named in the text.

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 trigger conditions ('when the user asks whether IndexNow is set up for a site, or why its IndexNow submissions are not taking effect'), explicit sequencing ('Check here before submit_indexnow_urls and whenever a submission fails'), and an explicit exclusion with alternative ('Not for past submissions: use list_indexnow_submissions'). Nothing is left to inference.

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