Update contact

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

The description goes well beyond annotations by disclosing the read-merge-write behavior, stating that unspecified fields retain their current values (including the required status). It also reveals the dry-run default and that confirm:true is needed to execute, which is a significant behavioral trait. The final 'Write' further clarifies mutability, complementing the idempotent and non-destructive annotations.

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 compact and front-loaded: three sentences that each add unique value. The first states the action, the second explains the merge behavior, and the third provides the critical dry-run/confirm workflow. No filler or redundancy.

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 (30 parameters, 1 required), the description covers essential behavioral context: the merge pattern, dry-run default, and write confirm. It does not explain response format or edge cases like missing contacts, but those are not expected given the absence of an output schema. The description is sufficient for an agent to invoke the tool correctly in most circumstances.

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?

With schema description coverage at only 37%, the description compensates by explaining the merge semantics that apply to all parameters: unspecified fields keep their current values. It specifically mentions the 'status' field behavior and confirm parameter, which are important. However, it does not describe individual fields beyond what the schema provides, and many parameters remain undocumented in either source.

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 opens with 'Edit fields on an existing contact,' clearly specifying the verb (edit) and resource (contact) and distinguishing from create operations. The read-merge-write behavior and dry-run default further differentiate it from sibling update tools by describing its specific update semantics.

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 provides clear context for when to use this tool: editing an existing contact with partial field updates. It explicitly explains the dry-run default and confirm:true requirement, which is critical usage guidance. However, it does not name alternatives like merge_contacts or exclusions (e.g., when a full replacement is needed), so it stops short of fully explicit when/when-not guidance.

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