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

readOnlyHint=true already tells the agent this is a safe read. Beyond that, the description discloses the return payload — contact details plus bookings as codes with created dates — which is genuinely useful since no output schema exists. It stops short of covering auth needs, error behavior, or whether the bookings list is paginated.

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 short sentences, front-loaded with the payload description; the endpoint citation is trailing reference material rather than a distraction. No filler, though the raw GET path is somewhat redundant for an agent.

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 one-parameter read-only tool with no output schema, the description supplies the missing return-shape information an agent needs. What remains uncovered — error cases, permissions, pagination of the embedded bookings — is minor for this tool class.

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 description coverage is 100% and the single parameter documents both the numeric id and the 'customer code' form. The description adds nothing beyond the schema and merely restates the endpoint path, so the baseline 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 ('Fetch one customer's contact details and their bookings'), which clearly separates it from list-style siblings like checkfront_list_bookings. It does not name checkfront_search_customers as the lookup alternative, so sibling differentiation is implicit rather than explicit.

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?

Usage is implied by the singular 'one customer' and the required customer_id, but there is no statement of when to prefer this over checkfront_search_customers or how to obtain a valid id in the first place. A competent agent can infer the case, but it is not spelled out.

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