contacts_update

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

Annotations already declare destructiveHint=true, idempotentHint=true and openWorldHint=true, so the bar is lower, but the description adds non-trivial context: email/phone fully replaces that collection rather than appending, and the '[permissions: contacts]' tag discloses the authorization scope. It stops short of describing the human-approval gate implied by the _approvalId parameter and destructiveHint.

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 short sentences plus a metadata tag, front-loaded with the update scope and then the field-replacement rule. No filler; the only marginal element is the version/permission tag, which still carries operational value.

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?

An output schema exists, so return values need no explanation, and the description covers the partial-update contract, replacement semantics and permission scope. The main omission is the approval/idempotency workflow, which is left entirely to the schema's parameter descriptions.

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 schema already documents all seven parameters, making 3 the baseline. The description reinforces which fields are updatable (name, email, phone) and clarifies replacement semantics for two of them, but adds no syntax or validation detail 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 (update) and resource (contact), and scopes it to 'only specified ... fields', which distinguishes a partial patch from a full replace. It never names a sibling such as contacts_create or contacts_search, so the differentiation comes from the name rather than the text.

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?

There is no explicit when-to-use, when-not-to-use, or alternative routing guidance. The phrase 'only specified' implies partial-update behavior, but an agent gets no signal about when this beats contacts_create or what prerequisites (existing contact id, approval) apply.

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