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

Annotations already declare readOnlyHint=true, and the description adds the HTTP method GET and the accounts model mapping, which is useful but not extensively beyond annotations. It does not describe response format or error behavior, but this is a simple read operation.

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 the main action, no redundant filler. The mention of endpoint and parameter support is efficient and directly useful.

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?

Given the low complexity, the description plus schema provide adequate context: what the tool does, the endpoint, and parameter behavior. Lacking output schema, but a simple resource fetch doesn't require extensive explanation.

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%, so all parameters are documented. The description only says 'Supports expand and fields', which adds no new semantics beyond the schema, justifying the baseline score.

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?

The description clearly states 'Fetch a single customer (Swell `accounts` model) by id', using a specific verb and resource, and distinguishes from list_customers by focusing on a single record. The endpoint and parameter support reinforce the tool's purpose.

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 description implies usage when a single customer id is known, providing clear context. It does not explicitly mention alternatives like list_customers, but the 'by id' qualifier gives sufficient guidance for selection.

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