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

readOnlyHint=true already tells the agent this is a safe read. The description goes further by naming the returned fields (contact details, first/last seen, visit counts, custom fields, tags) and the underlying endpoint, which is real value given there is no output schema. It still says nothing about auth scoping or error behavior when the id is unknown.

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 tight sentence plus the endpoint reference, with the payload description front-loaded before the API detail. Nothing is redundant, though the raw endpoint line is of marginal value to an agent that already has the tool.

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 simple one-parameter read with no output schema, the description supplies enough of the return shape to set expectations. It stops short of describing null/not-found behavior or nesting of custom fields and tags, which is a minor gap.

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% for the single memberId parameter, so the schema already carries the semantics. The description only restates 'by id' and embeds it in the endpoint template, adding no format, range, or sourcing guidance beyond what the schema provides.

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 (fetch) and resource (one customer, by id) and enumerates the payload it returns. The singular 'one customer by id' implicitly separates it from momence_list_members, but it never names that sibling, so the distinction is left to inference.

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 only implied: the 'by id' framing tells the agent a memberId is required and that this is a single-record lookup rather than a search. There is no explicit when-to-use, when-not, or pointer to momence_list_members / momence_get_current_user as alternatives.

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