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

Annotations already declare readOnlyHint and openWorldHint, so safety is partly covered, and the description adds genuinely useful context beyond them: the secret value is never returned, and the ability-string vocabulary is decoded. It does not describe output shape or any rate limits, but for a no-arg read that 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?

Two compact sentences plus a bare endpoint, front-loaded with the resource and the key safety fact (no secret returned). The permission-legend parenthetical is dense but earns its place since those strings are otherwise opaque.

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 output schema, the description carries the return-value burden and does so: name, permission abilities, timestamps, and the explicit exclusion of the secret. Complete enough for an agent to call it and interpret the result, though the exact timestamp fields remain 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 the baseline is 4; there is no parameter meaning for the description to clarify or obscure. The description instead spends its space on return-value semantics, which is the right allocation here.

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 ('the connected API token's name, permissions... and timestamps') and enumerates exactly what is returned. An agent can distinguish it from siblings like fathom_get_account or fathom_get_site without opening any 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?

'Good first call to know which tools will work' gives clear situational guidance for when to invoke it. There is no explicit statement of alternatives or when-not-to-use, but the sequencing advice is actionable.

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