Add or rename a WhatsApp contact

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

Annotations indicate a non-readonly write operation, and the description adds concrete side effects: name syncs to all linked devices and optionally to the phone's address book. It also clarifies that no other fields are stored, which helps set expectations beyond what annotations convey.

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 with the core purpose, then adds essential behavioral detail and a sibling distinction. Every sentence carries information without 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?

For a write tool with full schema coverage and no output schema, the description covers the primary use cases, side effects, and scope. It lacks explicit error or prerequisite information, but the tool is straightforward and the provided detail is sufficient for correct invocation.

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 coverage is 100%, so the baseline is 3. The description adds meaning by explaining that save_on_phone controls phone-book writes and by clarifying that the name field is for the contact name only (with notes going elsewhere). This enriches the 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 states a clear verb (save) and resource (WhatsApp contacts), and distinguishes two use cases: creating a new entry or renaming an existing one. It also explicitly routes non-name fields to set_contact_note, which differentiates it from that sibling.

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 clearly explains when to use the tool (new contact or rename) and gives an explicit exclusion for notes via set_contact_note. It doesn't enumerate all sibling tools but provides sufficient context to avoid the most common confusion.

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