Create Contact

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It fails to mention idempotency, duplicate handling, side effects (e.g., welcome emails), permission requirements, or what happens if a segment ID or topic subscription is invalid. Only the basic creation action is stated.

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 two sentences, front-loaded with the primary action, and includes the most important optional capabilities. No wasted words.

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?

Given the tool's complexity (7 parameters, nested objects, no output schema) and absence of annotations, the description is too sparse. It omits behavior around duplicates, error handling, response format, and usage context relative to sibling tools, leaving significant gaps for an AI agent.

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 parameters are well-documented in the schema. The description adds a high-level hint about optional segment assignment and topic subscriptions, but does not add detail beyond what the schema already provides. 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 states 'Create a new contact in Resend' with a specific verb and resource, and mentions optional segment assignment and topic subscriptions. It is clear, but it does not explicitly distinguish from sibling 'create-contact-import', which also creates contacts (albeit in bulk).

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?

No guidance is given on when to use this tool versus alternatives like 'update-contact', 'add-contact-to-segment', or 'update-contact-topics'. The description implies segment assignment and topic subscriptions are possible here, but does not clarify when to use this tool vs. the dedicated segment/topic mutation tools.

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