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

Annotations already cover readOnly/idempotent/non-destructive, but the description adds genuine behavioral context beyond them: any valid key works regardless of scopes, and the secret itself is never returned (only prefix and last_four). That is useful auth and output-shape disclosure not found in the structured fields.

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?

Front-loaded with the purpose, then scope/usage, then the return-fragment note. Every sentence carries information, though the opening line duplicates the title and the prose is slightly sprawling for a no-arg tool.

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 zero-parameter, no-output-schema tool whose safety profile is already in annotations, the description covers what the agent cannot infer: returnable fields, that the raw key is withheld, and the permission-free access model. Nothing needed to call it correctly 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?

The tool takes zero parameters, which is the baseline-4 case. There is nothing for the description to compensate for, and it correctly avoids inventing parameter detail.

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 ('describe') and resource ('the calling key') and then enumerates exactly what comes back: name, scopes, agent list, owning company, and rate limit. This clearly distinguishes it from siblings like get_agent or get_usage, so an agent can pick it without opening the schema.

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 states the trigger: 'Any valid key may call it... so it is the first call to make: to check a key works and see what it can reach.' This gives an unambiguous when-to-use condition (connectivity/scope verification) rather than leaving usage to inference.

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