Update Contact Topics

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

No annotations are provided, so the description carries the full burden. It states the action but does not disclose whether the topics array replaces the contact's existing subscriptions or merges, whether id/email must be provided (the schema only requires topics), or what the response contains. This is a significant transparency gap for a mutation tool.

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?

The description is one concise sentence that front-loads the action, resource, and identifier options. It contains no filler and every phrase earns its place.

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?

The tool has only 3 parameters and the schema covers all of them, so the description need not re-explain fields. However, for a mutation with no output schema and no annotations, it should ideally clarify whether topics are incrementally updated or fully replaced, and whether id or email is mandatory in practice. These gaps keep it at a middling score.

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 100%, so the baseline is 3. The description adds value by explicitly indicating that id and email are alternative ways to identify the contact, which is not clear from the schema alone (neither is required). It reinforces that topics are the subscription preferences to update.

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 ('update'), names the precise resource ('topic subscriptions for a contact'), and notes the product context ('in Resend'). It also distinguishes this tool from siblings like list-contact-topics and update-contact by focusing on the topic subscription operation.

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 implies the tool is used when you need to change a contact's topic subscriptions and mentions that the contact can be identified by ID or email. However, it does not explicitly say when NOT to use it or mention alternatives like list-contact-topics for viewing current subscriptions.

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