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resend

Email Sending MCP

by resend

Update Contact

update-contact

Update a contact's details in Resend using their ID or email address. Modify first name, last name, unsubscribed status, or custom properties.

Instructions

Update a contact in Resend (by ID or email).

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
idNoContact ID
emailNoContact email address
lastNameNoContact last name. Pass `null` to remove the contact's last name.
firstNameNoContact first name. Pass `null` to remove the contact's first name.
propertiesNoCustom property key-value pairs to update (e.g. { "company_name": "Acme" })
unsubscribedNoWhether the contact is unsubscribed from all broadcasts
Behavior2/5

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

No annotations provided, and the description does not disclose whether the update is partial or full replacement, behavior if both id and email are provided, or any side effects.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Single sentence that is to the point with no unnecessary words or fluff.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With 6 parameters (0 required), nested objects, and no output schema, the description is too brief. It lacks details on return values, success/failure behavior, and partial update semantics, making it insufficient for an agent to invoke confidently.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so parameters are well-documented in the schema. The description adds minimal extra context about identification by ID or email but does not override the schema's clarity.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the action (update), resource (contact), and system (Resend), and distinguishes from sibling tools like create-contact and remove-contact.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

No guidance on when to use this tool vs alternatives (e.g., when to update vs create or delete) or prerequisites like requiring either id or email. No exclusions or context provided.

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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