Create Contact Property

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 only states 'Create a new contact property' without explaining potential side effects such as duplicate key errors, immutability of the property type after creation, or any permission requirements. This is a significant 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 two sentences, front-loaded with the action, and contains no filler. The first sentence states what the tool does; the second defines the domain concept with examples. Every word 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 is simple with three well-documented parameters, but the description lacks important context such as what happens when a property with the same key already exists, whether the type is immutable after creation, or what the successful response contains. The schema covers parameter details, but the absence of annotations and output schema leaves behavioral gaps that the description does not fill.

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 schema already documents all three parameters. The description adds minor value by giving examples of property keys and explaining what a contact property is, but it does not provide additional semantics for the 'fallbackValue' parameter beyond what the schema offers. This meets the baseline for high coverage.

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 clearly states 'Create a new contact property in Resend' with a specific verb and resource, and provides illustrative examples (e.g., company_name, plan_tier) that clarify what a contact property is. This distinguishes it from sibling CRUD tools like update-contact-property or list-contact-properties by focusing on the creation action.

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 about when to use this tool versus alternatives. It does not mention that for modifying an existing property one should use update-contact-property, nor does it address scenarios like checking for existing keys before creation. The only implied usage is 'create a new property,' which is not explicit.

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