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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds value beyond that by disclosing what the response contains (contact details, Shopify customer id, subscription/charge counts) and mapping the call to REST GET /customers/{id}, though it omits auth or rate-limit context.

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 tightly written sentences with the core action front-loaded and the REST endpoint as a trailing reference. No filler or redundancy.

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-resource getter with one required param and no output schema, the description usefully sketches the returned fields, which partially compensates for the missing output schema. Minor gaps remain around permissions and error behavior, but nothing essential for invocation 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?

Schema coverage is 100% and the single 'id' parameter is documented as 'Customer id.' The description adds only the phrase 'by id', which is already conveyed by the schema, so the baseline of 3 applies.

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 customer by id') and the word 'single' distinguishes it from the sibling recharge_list_customers without needing to inspect the schema. It also enumerates what the resource contains (contact details, Shopify customer id, counts).

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 'by id' implies this is for retrieving one known customer rather than enumerating them, which softly contrasts with recharge_list_customers. However, no explicit when-to-use, when-not-to-use, or named alternative is provided.

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