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

Annotations already declare destructive, idempotent, non-read-only behavior, so the description need not repeat those. It adds meaningful context beyond the annotations by disclosing that contact details, tax ids and addresses are never returned and by summarizing which fields are returned after an update.

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 with no wasted wording, and the usage trigger is front-loaded before the exclusion and return details.

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?

Given rich annotations, an output schema and full schema descriptions, the description covers the remaining gaps: when to use it, what it is not for, and the sensitive return-field policy. Nothing material 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%, including the optimistic concurrency guard on expectedLastEditTime and the address merge behavior, so the schema already carries parameter meaning. The description only lists updatable fields and adds no syntax or format details 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?

The description names a specific verb and resource ('change a customer's name, email, phone, tax id, address or language') and explicitly excludes adding a new customer. An agent can distinguish this from create_customer without opening either 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?

It gives a clear when-to-use trigger and a when-not exclusion ('Not for adding a new customer'). It does not name the sibling alternative explicitly, but the exclusion routes the agent away from the wrong tool.

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