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 the annotations by enumerating the categories of data returned (addresses, contacts, terms, balance, custom fields) and citing the underlying endpoint, which is meaningful for a tool with no output schema. It does not mention error/not-found behavior, keeping it short of a 5.

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?

A single front-loaded sentence plus an endpoint citation, with zero filler. The resource and key returned fields come first, and the HTTP path is compact trailing context.

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 tool with readOnlyHint annotations, the description covers the essentials, and its field enumeration partially compensates for the absence of an output schema. It stops short of describing pagination/expansion or failure modes, but nothing critical for correct 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 description coverage is 100% (the 'id' parameter is documented as the numeric customer_id), so the schema carries the parameter burden. The description's 'by customer_id' matches and mildly reinforces the schema but adds no format, range, or lookup-detail beyond it, making the baseline 3 appropriate.

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 one customer by customer_id') and enumerates the fields returned (company, status, addresses, contact, terms, balance, custom fields), which clearly separates it from list_customers and the other get_* siblings. The endpoint notation 'GET /customer/{customer_id}' reinforces the single-record scope.

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 'one customer by customer_id', so an agent can infer this is the single-record lookup versus chargeover_list_customers. However, no explicit when-to-use, prerequisites, or named alternative is given, so guidance remains inferential rather than stated.

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