Send SMS Message

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

Beyond the annotations, the description discloses that this 'sends a REAL SMS' — a real-world side effect that annotations alone do not convey — and that it operates by driving the Phone Link UI through clicks. It also specifies failure behavior ('Returns sent=false with error message if any UI element can't be found') and lists concrete failure modes. Nothing contradicts readOnlyHint=false, openWorldHint=true, idempotentHint=false, or destructiveHint=false.

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 front-loaded with the core purpose and organized into labeled sections (Args, Returns, Warning, Error Handling), making it easy for an agent to scan. It runs longer than the minimum, but the real-SMS warning and failure-mode list carry critical safety and recovery information that earns their place.

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?

With no output schema present, the description correctly specifies the return shape ({sent, recipient, message}). It covers purpose, mechanism, parameters, return format, real-world risk, and failure recovery — everything needed to invoke a 2-parameter side-effectful tool safely.

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 100%, so the schema already fully documents both parameters. The description's Args section largely restates the schema ('Contact name or phone number', max 1600 chars) without adding new semantic meaning, so the baseline 3 applies.

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 opening line, 'Send an SMS message through Phone Link's UI,' provides a specific verb and resource, and the next sentence ('Opens a new message, types the recipient and message text, and clicks Send') makes the mechanism unambiguous. The purpose is self-evidently distinct from the sibling get_* tools, phonelink_make_call, and phonelink_launch_app even without naming them.

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 implies when to use it — when a real SMS must be sent from the phone — but never explicitly contrasts it with phonelink_make_call (voice) or the read-only get_* tools. The error-handling notes (phone not connected, Messages tab not loading) give situational context about when it may fail, but explicit when-to-use/when-not-to-use guidance is absent.

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