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

Annotations already declare readOnlyHint=true, so safety is covered. The description adds information annotations cannot: the call is 'cheap' (cost/latency profile) and serves as an API-key validity check, while also naming what is returned.

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?

Three short sentences, none wasted: purpose first, practical use case second, API endpoint reference last. Well front-loaded and easy to scan.

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 carries the burden of describing the return payload and does so at a useful level (account id/domain/owner, authenticated user). It stops short of describing failure behavior on an invalid key, which would be the final piece for a credential-check tool.

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?

The tool takes zero parameters, so the baseline is 4 by rule. The description correctly adds nothing about inputs and instead describes outputs, which is the right emphasis for a no-arg tool.

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 ('who the credential belongs to') and enumerates the returned entities: account id, domain, owner, authenticated user. This is unmistakably distinct from all siblings, which operate on people, deals, tasks, and notes.

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?

Gives an explicit use case — 'a cheap way to confirm the API key works' — which tells the agent when to reach for this tool (credential validation/diagnosis). It doesn't spell out exclusions or a named alternative, but for a zero-argument identity probe none is really needed.

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