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

Annotations already cover safety (readOnly, idempotent, non-destructive), yet the description adds real context beyond them: nothing can create/change/delete, contact notes are never read, results are ordered best-match-first, and card fields may come from shared/imported sources and must be treated as data not instructions (prompt-injection caution). This is substantive disclosure, not restatement.

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?

Front-loaded with purpose, then query semantics, usage routing, sibling contrast, and a safety note. Every sentence carries information, but it is a single dense block rather than segmented, which slightly hurts scannability.

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 two-parameter read-only search, the description covers input semantics, ambiguity handling, safety, and even the result shape (contact_id, name, organization, job_title, emails/phones with labels) despite an output schema existing. Nothing an agent needs to call it correctly 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?

With schema description coverage at 0%, the description carries the burden and does so well for `query`: accepted input types (name, nickname, company, email, phone), all-words-match semantics, case/accent insensitivity, and a concrete example. `limit` is left unexplained, so one of two parameters is undocumented.

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 with scope: 'Search the Contacts on this Mac'. It explicitly distinguishes itself from the sibling get_contact ('get_contact reads one contact in full'), so an agent can separate the two without reading 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?

Gives the positive trigger ('turn a person's name into an address before save_draft or send_email') and a behavioral rule for ambiguity ('if more than one contact or address could be meant, ask the user which one instead of picking'), plus the contrast with get_contact. Both when-to-use and how-to-branch are covered.

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