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

Beyond the destructiveHint annotation, the description spells out exactly what is destructive: numbers are replaced wholesale, an omitted default_outbound_number_id clears it, while omitted names/company/email keep stored values. This is precisely the behavioral context an agent needs for a PUT-style update.

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 dense but front-loaded: operation type and semantics first, then required replacement behavior, then omission rules, then the read-first instruction and endpoint. Every sentence carries necessary information.

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?

With no output schema, the description still gives enough behavioral detail for safe invocation: required fields, replacement semantics, omission behavior, immutability of the system contact, and a prescriptive read-before-write workflow.

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 only 43%, but the description compensates by explaining that numbers is required and replaces all stored numbers, and that omitted default_outbound_number_id clears it whereas other omitted fields retain their value. This adds critical semantics not fully captured in the schema.

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 a specific write operation (update a contact) with PUT semantics and endpoint, clearly distinguishing it from read tools like rinkel_get_contact and from create/delete siblings. An agent can immediately tell this is a mutation tool.

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?

It explicitly instructs the agent to read the contact first via the named sibling rinkel_get_contact and resend what must stay. It also states the system contact cannot be changed, giving a concrete exclusion.

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