send_sms

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It states the action ('Send an SMS message') and return type, but lacks critical details: it doesn't specify permissions required (e.g., SMS sending capability), potential side effects (e.g., network usage, user notifications), error conditions (e.g., invalid numbers, network failures), or rate limits. For a mutation tool with zero annotation coverage, this is a significant gap in transparency.

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 appropriately sized and well-structured, with a clear purpose statement followed by parameter and return sections. Every sentence earns its place by conveying necessary information without redundancy. It could be slightly more front-loaded by integrating parameter hints into the opening sentence, but overall it's efficient and readable.

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 moderate complexity (a mutation with 2 parameters), no annotations, and an output schema (which covers return values), the description is minimally complete. It defines the action and parameters but lacks behavioral context (e.g., permissions, errors) and usage guidelines. The output schema handles return documentation, but the description should do more to compensate for the absence of annotations, making it adequate but with clear gaps.

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%, so the schema provides no parameter descriptions. The description compensates by listing both parameters with basic types ('phone_number (str): Recipient phone number', 'message (str): Message content'), adding essential meaning beyond the bare schema. However, it lacks format details (e.g., phone number formatting like E.164, message length limits), leaving some semantic gaps. This partial compensation justifies a baseline score.

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 tool's purpose with a specific verb ('Send') and resource ('SMS message'), making it immediately understandable. It distinguishes from most siblings (e.g., 'call_phone', 'get_sms') by focusing on sending rather than calling or retrieving. However, it doesn't explicitly differentiate from potential messaging alternatives like 'input_text' or 'set_clipboard_text', which slightly limits sibling distinction.

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 no guidance on when to use this tool versus alternatives. It doesn't mention prerequisites (e.g., device permissions, network connectivity), exclusions (e.g., character limits, supported regions), or comparisons to similar tools like 'input_text' for on-device text entry. This leaves the agent with minimal context for appropriate selection.

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