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

Annotations already declare write, destructive, idempotent, and open-world behavior. The description adds meaningful nuance beyond that: it explains the read-before-write flow, that omitted fields are passed back unchanged, and that contact details are immutable via the API. It doesn't cover permissions or error behavior, but it substantially enriches the behavioral picture.

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?

Four tightly packed sentences, front-loaded with the write intent and affected fields. Every sentence earns its place: mutability scope, read-modify-write behavior, the contact-detail exclusion, and the endpoint.

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 9-parameter mutation tool with no output schema, the description covers the essential behavioral details: what can change, what happens to omitted fields, what cannot change, and the HTTP endpoint. It lacks return-value or error details, but those are minor given the annotations and lack of an output schema.

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%, so the baseline is 3, but the description adds real semantic value by explaining that both names are required on update and that omitted values are auto-filled from the current record. It also flags which fields are mutable (title, name, marketing consent, contact preferences) and which are not (email/phone/address), which goes beyond the schema's per-parameter 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?

States a specific verb and resource ('change a person's... in Street') and enumerates the affected fields. The 'WRITE:' prefix and PATCH endpoint make it unmistakably distinct from read-only siblings like street_get_person and street_list_people.

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?

Clearly scopes the tool to changing a person's title, name, marketing consent, or contact preferences, and explicitly excludes contact details ('email, phone, address cannot be changed through the API'). It doesn't name an alternative tool for contact-detail changes, which keeps it from a 5.

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