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

Annotations already declare non-destructive, idempotent, non-read-only, so safety is covered. The description adds the 'you own it' authorization constraint and the compare-and-set conflict semantics — useful beyond annotations. But it omits the critical behavior for an 11-field update: whether omitted fields are left unchanged (partial/PATCH) or cleared (replace), and what a conflict response returns.

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?

One sentence, front-loaded with the action and scope, with the optional mode in parentheses. No waste, though it errs toward under-specification rather than richness.

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 mutation tool with 11 parameters, no output schema, and low schema coverage, the description is too thin. Missing partial-vs-full update semantics, which fields are writable, and conflict/error behavior leaves real gaps 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 only 18% across 11 parameters, so the description must compensate, yet it explains nothing beyond expected_updated_at, which the schema already documents in full. The 9 updatable fields and the two enums (source, status) get no treatment in the description.

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?

Clear verb+resource: 'Update a contact you own'. The ownership qualifier narrows scope meaningfully. It doesn't distinguish itself from contact_upsert or contact_create by name, but the verb 'update' vs 'create'/'upsert' is reasonably self-evident.

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?

Only guidance is the ownership precondition and an optional compare-and-set mode. No statement of when to use this instead of contact_upsert (which likely also handles existing records) or how it relates to contact_delete/contact_read. An agent must guess between update and upsert.

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