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 meaningful context beyond that: the exact returned fields, the low-cost nature of the call, and its credential-check purpose. It does not describe error behavior when credentials are invalid, but the extra disclosure exceeds the annotation baseline.

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?

Two efficient sentences plus the endpoint reference: what it returns first, why to call it second, raw API mapping last. Every clause carries information and the most important content is front-loaded.

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 read tool with no output schema, the description compensates by naming the returned fields (name, base currency, default tax rate), plus the endpoint and purpose. An agent has everything needed to call and interpret 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?

The tool takes zero parameters, so per the rubric the baseline is 4. There is nothing for the description to disambiguate or document beyond the empty schema.

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), resource (the Unleashed company these credentials belong to), and even enumerates the returned fields (name, base currency, default tax rate). It is unambiguous against siblings like unleashed_get_customer or unleashed_get_product because it is the only company-level tool, and it maps to a concrete endpoint (GET /Companies).

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?

"A cheap way to confirm the API id, key and signature are right" gives a clear calling context: credential validation. There are no sibling alternatives to route between, and no explicit when-not-to-use guidance, so it falls just short of a 5.

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