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

readOnlyHint=true already declares the safety profile, but the description adds real context beyond it: the result is scoped to the calling API key's identity, the response fields are enumerated, and calling it is framed as 'cheap' (no meaningful cost/side effects). It does not discuss error behavior (e.g. whether an invalid key surfaces as an error here), which keeps it at 4.

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 sentences, front-loaded with what is returned before the rationale, and it closes with the REST endpoint for traceability. No filler or repetition of the title.

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 input parameters and no output schema, the description carries the whole burden and does so by listing the returned fields, which an agent otherwise could not know. 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 sets the baseline at 4; there is nothing for the description to disambiguate. It correctly avoids inventing parameter guidance that does not exist.

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 and resource ('Fetch the user this API key acts as') and enumerates the returned fields (id, name, company, default location, permissions). The key-scoped framing cleanly distinguishes it from the sibling shopmonkey_list_users, which returns a collection rather than the identity behind the credential.

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 gives two use cases: 'a cheap way to confirm the key works and to find your locationId.' This tells an agent when the tool is worth calling. It stops short of naming an alternative to use instead in other situations (e.g. list_users for enumerating teammates), so it is a 4 rather than a 5.

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