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

Annotations already provide readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the agent knows this is safe and deterministic. The description adds context about the return content (limits, usage, subscription), but does not describe exact return format or any potential caveats such as rate limits. Given the annotations carry the safety profile, a 3 is acceptable.

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?

The description is a single sentence of 12 words with no redundancy, directly stating the resource and its contents. It is efficient and front-loaded with the core action. Every word earns its place, making it highly concise and well-structured.

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?

Given the tool's simplicity (one parameter, no output schema) and the annotations providing safety cues, the description is reasonably complete. It does not detail the exact return structure, but as an account overview, its scope likely matches the described contents. The lack of an output schema gives room for more detail, but the description covers the essential context for an agent to know when to call it.

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 only one parameter, api_key, and it is fully described in the schema at 100% coverage. The description adds no additional meaning to the parameter beyond what the schema already provides. Since the schema covers the parameter entirely, a baseline score of 3 is appropriate.

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?

The description clearly states the tool's purpose with a specific verb and resource: 'Get account plan details'. It specifies that it includes limits, usage, and subscription information. This distinguishes it from other get tools in the sibling list, which are all about campaigns, contacts, templates, etc. Its scope is unique and unambiguous.

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?

The description implies usage when account subscription or usage information is needed, but does not provide explicit guidance on when to use this tool versus alternatives or mention any exclusions. Given the subject matter, it's likely the only tool for account overview, but the description does not explicitly state this. A modest score is appropriate.

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