Look up a person in Contacts by name and return their sendable handles before sending a message, useful when you know a name but not a number.
Look up a person in Contacts by name and return their sendable handles. Use before send_message when you know a name but not a number.
| Name | Required | Description | Default |
|---|---|---|---|
| name | Yes |
Changes observed during successful MCP inspections.
v0.3.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true and openWorldHint=false, so safety and scope are covered without the description. The description adds real value by disclosing the return content ('sendable handles'), which matters because there is no output schema. It does not describe ambiguity or not-found behavior, keeping it short of a 5.
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, zero filler, with the core action front-loaded and the sequencing hint second. Nothing could be cut without losing information.
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, read-only lookup with no output schema, the description covers purpose, timing, and return content. It omits edge-case behavior such as multiple matches or no match, which is a minor gap given the tool's simplicity.
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 0% for the single 'name' parameter, so the description must compensate. 'By name' confirms the lookup key is a person's name in Contacts, which is slightly more than the bare schema, but it gives no format or matching guidance (full name vs. partial, ambiguity handling).
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 ('Look up a person in Contacts') plus the output ('sendable handles'), which distinguishes it from send_message and the other siblings. An agent can tell immediately this is a name-to-handle resolver, not a messaging tool.
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?
Explicitly names the sibling it precedes ('Use before send_message') and the selecting condition ('when you know a name but not a number'). The inverse condition — you already have a number — is implicitly covered by that phrasing, so routing is unambiguous.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.