Update Contact Property

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

No annotations are provided, so the description carries full behavioral disclosure burden. It adds a key constraint (key/type immutable) beyond schema, but lacks information on error behavior, authorization requirements, or effects of nonexistent IDs. Some transparency, but not comprehensive.

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?

Two sentences, zero waste. The first sentence clearly states the action and resource; the second adds a critical limitation. Front-loaded and efficient.

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 simple 2-parameter update tool with no output schema or nested objects, the description covers the essential purpose and the most important behavioral constraint. Missing details like return format or error cases are minor given the tool's simplicity.

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% with meaningful descriptions for both parameters. The tool description reinforces that only fallbackValue is mutable, but adds no new parameter-level insight 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?

Description states a specific action (update) on a specific resource (contact property in Resend) and explicitly clarifies the scope (only fallback value can be changed). This clearly distinguishes it from sibling tools like create-contact-property or update-contact.

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 when to use the tool (when updating a contact property's fallback value) and what cannot be done (key/type change), but does not explicitly name alternatives like create-contact-property for new properties or remove-contact-property for deletion. Context is clear but no direct comparisons.

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