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

Annotations already provide destructiveHint=true, so the description does not need to restate that. It adds value by disclosing partial-update semantics ('Only provided fields are changed') and the specific REST method, going beyond the annotation.

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, front-loaded with the core action, followed by the key behavioral note and REST hyperlink. No filler or redundant detail.

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 update tool with full schema coverage and a destructive-hint annotation, the description covers the essential behavior needed for invocation. It does not describe return values or errors, but those are not required for selection or basic usage.

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?

All 7 parameters have individual descriptions in the schema (100% coverage), so the description does not need to repeat them. It adds general update context but no per-parameter semantics beyond 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 clearly states the verb and resource: 'Update fields on an existing contact.' The phrase 'existing contact' distinguishes this update tool from create/get/list tools among the siblings.

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 mentions that 'Only provided fields are changed,' which is a useful partial-update nuance, but it does not explicitly state when to prefer this over aircall_create_contact or aircall_get_contact, nor does it name alternatives.

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