find_contact

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

With no annotations, the description carries the behavioral burden. It discloses that matching is case-insensitive substring containment, that the query can match name or number, and that all matching contacts are returned. This goes beyond a simple one-line summary, though it omits details like result ordering, pagination, or empty-result behavior.

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 deliver the core action, matching behavior, and practical use cases without filler. The most important behavioral details are front-loaded, and every sentence contributes meaning.

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 one-parameter search tool with no output schema, the description is nearly sufficient: it explains what is searched, how matching works, and what is returned. The main gap is not mentioning the alternative list_contacts or the shape of returned contact objects, which would round out agent decision-making.

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?

The single parameter already has a clear schema description: 'Name or phone number fragment to search for.' The tool description adds value by specifying case-insensitive contains semantics and that both name and number are searched. With 100% schema coverage, this extra context justifies a score above baseline.

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 specifies a clear verb and resource: 'Search contacts by name or phone number fragment,' and clarifies that it returns matching contacts via substring matching. It is clearly distinct from list_contacts in function, though it does not explicitly name or contrast a sibling tool, so it stops short of full differentiation.

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?

The description gives explicit use cases: 'look up a phone number when you only know a name' and 'verify a contact exists.' It provides clear context for when to use the tool, but it does not mention alternatives or when not to use it, such as choosing list_contacts for unfiltered contact listing.

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