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

Goes well past the annotations: discloses partial-update semantics ('only the fields you pass are sent'), that passed values overwrite existing ones, the API-key requirement, the 'edit customer' webhook side effect, and the underlying HTTP verb/path. Annotations already flag destructive/idempotent; the description adds the operational consequences.

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?

Five compact clauses, front-loaded with the WRITE marker and the core semantics before auth and side-effect details. No filler sentences.

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?

Covers what matters for a 16-parameter mutation: partial-update behavior, auth, overwrite risk, and side effects, with all parameters documented in the schema. It does not say what the response contains (no output schema exists), which is the one 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 description coverage is 100% across all 16 parameters, and the schema itself points to phppos_list_customers for person_id, so the schema carries the parameter burden. The description only generalizes that supplied fields are sent, adding no per-field meaning beyond the schema.

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 ('change fields of an existing customer') and pins the target with the endpoint POST /customers/{person_id}. The 'WRITE:' prefix and 'existing customer' wording separate it cleanly from phppos_create_customer and phppos_get_customer without needing the schema.

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?

Gives clear conditions for use: only the supplied fields are sent, so it is a partial update, and a Read/Write API key is required. It does not name alternatives (e.g. use phppos_create_customer for new records, phppos_get_customer to inspect before editing), so the bar for a 5 is not met.

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