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

Annotations declare readOnlyHint=true, and the description reinforces this with a non-destructive, key-scoped read ('the company this key belongs to') plus a cost signal ('cheap'). With no output schema, its enumeration of return fields and the multi-location caveat adds genuine behavioral value.

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 core action and resource, followed by a short usage note and the endpoint reference. Slightly dense with a mildly awkward '(multi-location) its locations' clause, but every sentence carries information.

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-param read with no output schema and readOnlyHint already set, the description covers enough: it names the return fields, notes key scoping, and flags multi-location behavior. Only the exact response structure remains unspecified.

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 there is nothing for the description to document and the baseline is 4. It correctly adds no spurious parameter discussion.

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 (Fetch) and resource (the company this key belongs to) and enumerates the returned fields (name, contact details, address, time zone, zip codes, locations). No sibling tool targets the company resource, so an agent can route to it unambiguously.

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?

Provides an explicit use case: 'A cheap way to confirm the key works.' That gives clear context for when to reach for it, but offers no when-not guidance or named alternatives (none exist among siblings, which slightly softens the gap).

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