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

Annotations only declare destructiveHint=true; the description goes well beyond that by disclosing that each field is a separate API call (with the actual endpoints), that the calls execute in a fixed order (name, email, phone), and that execution stops at the first failure — i.e. the operation is non-atomic and can partially succeed. That is exactly the behavioral context an agent needs before invoking a mutation.

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 dense sentence with the core purpose front-loaded, followed by the parameter interdependency and the failure semantics. No filler, no repetition of the title, and every clause carries information the agent needs.

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 5-parameter mutation with no output schema and thin annotations, the description covers the highest-risk unknown (non-atomic partial failure) and the field-combination rules. It stops short of noting permission requirements or what state the member is left in after a mid-sequence failure, which would be the remaining 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 coverage is 100% and the schema already encodes the firstName/lastName interlock, so the baseline is 3. The description still adds real value by tying each parameter to a distinct endpoint call and an execution order, and by restating the and/or combination semantics (any subset of rename/email/phone).

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: "Correct a customer's contact details", with the concrete fields it touches (name, email, phone) spelled out. It doesn't name a sibling alternative (e.g. vs. momence_create_member), but the operation is unambiguous from the title and first sentence.

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 "Correct a customer's contact details" and the field-combination rules, but there is no explicit when-to-use/when-not guidance and no routing to alternatives such as momence_create_member or momence_get_member. An agent can infer the context but must supply the exclusions itself.

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