create_contactCreate a new contact. A contact needs at least a name; email, phone_number and identifier must each be unique in the account. This does not start a conversation.
| Name | Required | Description | Default |
|---|---|---|---|
| name | Yes | ||
| No | |||
| identifier | No | ||
| phone_number | No | E.164, e.g. +573001112233. | |
| custom_attributes | No | Values for the account custom attributes, by key. | |
| additional_attributes | No | Free-form details such as company_name or city. |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations cover the safety profile (readOnlyHint=false, destructiveHint=true, idempotentHint=false) but say nothing about data constraints. The description adds genuinely new behavioral context: email, phone_number, and identifier must each be unique within the account, which predicts conflict failures an agent must anticipate.
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 short sentences, front-loaded with the action, followed by constraints and then the sibling-exclusion. No filler and every clause carries 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 create tool with no output schema, the description covers the required field, uniqueness failure modes, and the scope boundary against conversations. It omits any guidance on the two nested attribute objects and on what a conflict response looks like, which keeps it from being fully complete.
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 50% and the description compensates partially by stating the required field and the uniqueness semantics for email, phone_number, and identifier — meaning the schema does not carry. However, custom_attributes and additional_attributes (both nested objects) are never mentioned, leaving the non-obvious parameters undocumented in both places.
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 opens with a specific verb+resource ('Create a new contact') and immediately scopes what a contact minimally requires. The closing line 'This does not start a conversation' separates it from conversation-creating siblings such as new_conversation or create_a_new_message_in_a_conversation.
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?
It states the prerequisite (at least a name) and an explicit exclusion (does not start a conversation), which tells an agent when not to reach for it. It stops short of naming the adjacent alternatives (update_contact for edits, search_contacts for lookup), so it is clear context without full routing.
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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