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

The annotations already declare destructiveHint=true, and the description reinforces this by stating 'This MODIFIES live store data,' adding the production-impact context beyond the raw flag. 'Provide only the fields you want to change' also discloses partial-update behavior, which is meaningful and not present in the structured metadata.

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 sentences contain the purpose, the live-data warning, the endpoint reference, and the key usage instruction. Every clause earns its place, and the most important information is front-loaded.

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 four-parameter update with no output schema, the description covers the essential operational aspects: what is updated, that it is a PATCH to /customers/{id}, the destructive nature on live data, and the partial-update rule. It lacks details such as idempotency or error handling, but these are not critical for correct invocation.

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%, so the baseline is 3. The description adds value by clarifying the PATCH semantics—'Provide only the fields you want to change'—which tells the agent that optional params can be sent individually and omitted fields are preserved. This is important behavioral nuance beyond the schema's 'New ...' descriptions.

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?

The description opens with 'UPDATES a customer's profile fields' and explicitly lists first_name, last_name, and email, making both the verb and resource precise. This clearly differentiates the tool from the read/list siblings and from update_subscription by targeting the customer resource.

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?

'Provide only the fields you want to change' gives clear, actionable guidance for the PATCH-style partial update, and the warning 'This MODIFIES live store data' sets expectations for when to invoke it. It does not explicitly name alternative tools or exclusions, but the context is unambiguous enough that an agent can select it correctly.

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