Create a named contact list owned by the authenticated user. If a list with the same name already exists, returns its list_id instead of creating a duplicate.
| Name | Required | Description | Default |
|---|---|---|---|
| name | Yes | List name (max 120 characters). | |
| description | No | Optional list description (max 1000 characters). |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Beyond the idempotentHint annotation, the description explicitly states the exact idempotency behavior: if a list with the same name exists, it returns the existing list_id instead of creating a duplicate. This is valuable behavioral context directly actionable for an agent.
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 concise sentences: the first states the core purpose, the second adds the critical idempotency behavior. No filler, front-loaded 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 simple creation tool with two well-schema'd parameters)Skip the description covers purpose and edge-case behavior. The only slight gap is not specifying the exact response shape beyond returning list_id, but that's minor given the no-output-schema context.
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 100%, so parameter semantics are fully documented in the schema. The description adds no extra parameter detail but doesn't need to; baseline 3 is appropriate.
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 uses a specific verb ('Create'), names the resource ('named contact list'), and specifies ownership by the authenticated user, making the tool's purpose immediately clear. It also distinguishes itself by noting the duplicate behavior, which prevents confusion with similar creation tools.
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 clearly implies when this tool is appropriate—whenever a lead list needs to be created—and adds the key usage nuance that existing lists are reused rather than duplicated. It doesn't explicitly reference sibling tools, but the context is clear and no exclusions are needed.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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