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

readOnlyHint=true already covers the safety profile, so the description's added value is real: it discloses that the payload is JSON:API '{ data }' and that it contains PII, which is behaviorally important for an agent handling the response (e.g. avoiding unnecessary logging). It stops short of covering auth requirements, 404 behavior, or rate limits.

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?

One sentence plus a short REST mapping, with the purpose front-loaded before the endpoint detail. Efficient; the endpoint hint is marginal but useful for cross-referencing, so not quite a 5.

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 single-parameter read tool with no output schema, the description supplies the essential missing piece — that the response is JSON:API with a data envelope containing PII. Auth/permission requirements and error semantics remain unstated, keeping it below a 5.

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?

Schema coverage is 100% with a single, fully documented account_id parameter, so the schema carries the semantics. The description only restates the by-id lookup and adds no format or prefix detail beyond the schema's 'act_...' example — baseline 3.

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 ('Get a single account by id'), then clarifies the domain meaning ('the persistent identity record for an end user') and names the underlying REST route. This cleanly separates it from persona_list_accounts without the reader needing to open either 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?

The phrase 'a single account by id' implies the usage context (retrieve one record when you already have its id), but it never states when to prefer this over persona_list_accounts or what to do if the id is unknown. Implied usage only, no exclusions or prerequisites.

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