send_message

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

With no annotations, the description carries the full burden and does well: it discloses AppleScript reliance, iMessage vs SMS/RCS behavior, auto-detection fallback, and the confirmation requirement. It could be more transparent about failure behavior or permissions, but the key behavioral traits are clearly stated.

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: two sentences, front-loaded with the core action, and no filler. The IMPORTANT warning earns its place because it encodes a critical safety workflow. Redundancy with the schema is minimal and acceptable.

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 single-send tool with moderate complexity, the description covers the main invocation context: recipient types, service selection, fallback behavior, and confirmation. It doesn't detail delivery outcomes or error paths, but those are plausibly covered by sibling tools and are not essential to selecting and invoking this tool correctly.

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 baseline is 3. The description adds meaningful context beyond the schema by explaining blue/green bubble semantics, the auto fallback behavior tied to the service parameter, and reinforcing the confirm parameter's real-world purpose with the 'IMPORTANT' note.

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 a specific verb and resource: 'Send an iMessage or SMS/RCS to a contact.' It clearly distinguishes itself from send_message_batch by describing a single message to a single contact, and adds concrete context with blue/green bubble terminology and AppleScript mention.

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 usage for sending one message and provides the important workflow requirement to show content and get confirmation. However, it does not explicitly say when to use this tool versus siblings like send_message_batch or detect_message_service, nor does it list exclusions or alternatives.

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