Find a contact

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

Annotations already declare readOnly, idempotent, non-destructive, openWorld; the description adds value beyond them by disclosing the null-return behavior when nobody matches and the 'con_...' id format needed downstream. It does not mention pagination or whether 'one contact' implies unique match on phone vs external_id.

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?

Three compact sentences: what it does, edge-case return, and the downstream handoff. Every sentence earns its place and the lookup semantics are front-loaded.

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 needn't be explained, yet the description still flags the null case helpfully. The only gap is behavior when zero required params are supplied (both phone and external_id absent).

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 only 50% — external_id has no schema description — but the description compensates by defining it as 'the id your own system gave the customer' and clarifying that phone is E.164 format. It still does not say whether the two params are mutually exclusive or which takes precedence.

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 ('Find one saved contact') plus the exact lookup keys (phone in E.164, or external_id). It is immediately distinguishable from sibling list/search tools like sendkuy_list_messages or sendkuy_get_account, which return collections or account data rather than a single contact.

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 context for use implicitly and explicitly: look up a contact, then use the returned 'con_...' id as a recipient in sendkuy_send_message. That names the downstream alternative and the handoff. It lacks an explicit 'when not to use' (e.g., when you already have the contact id or need to list all contacts).

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