Send a contact card

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

Annotations already declare readOnlyHint=false and openWorldHint=true, so the agent knows this is a non-read-only, external-facing action. The description adds a useful side-effect clarification (no contact is saved), but does not cover other behavioral details such as authentication needs, rate limits, or what exactly is written to the chat.

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 short sentences, front-loaded with the core action, and no wasted words. The second sentence adds important behavioral context without bloating the definition.

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 tool with four undocumented parameters and no output schema, the description is too thin. It does not give the agent enough information to correctly supply required values (e.g., chat identifier format, phone format), leaving critical invocation details to guesswork.

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 0% across four parameters. The description vaguely mentions 'phone contact' and 'into a chat,' which loosely map to phone and chat, but it does not explain firstName/lastName requirements, phone format, or what values the chat parameter accepts. It does not compensate for the missing schema documentation.

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?

States a specific verb ('Send') and resource ('phone contact (vCard)') with scope ('into a chat'), and distinguishes itself from contact-saving siblings by noting 'Nothing is saved to your contacts list.' An agent can tell it apart from send_message and add_contact without opening schemas.

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?

Provides implicit context (send a contact card) and a negative guideline ('Nothing is saved to your contacts list'), which helps exclude use for saving contacts. However, it does not explicitly name an alternative or state a positive when-to-use condition, leaving the agent to infer the choice from the description alone.

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