createTextMessage

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

With no annotations available, the description carries the full burden. It discloses that the tool only records, does not deliver, and requires specific environment variables ('FUB_SYSTEM + FUB_SYSTEM_KEY'). This gives important behavioral context about side effects and restrictions, though it does not detail return values or error conditions.

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 two sentences: the first states the core function, the second adds critical non-delivery and auth restrictions. Every sentence earns its place, and the main action is front-loaded. There is no redundant information.

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?

The tool has moderate complexity with 7 parameters, all documented in the schema. The description provides essential operational context (logging vs sending, restricted access) that is not in the schema. Given no output schema, the description is reasonably complete, though it could mention the response type or success/failure behavior.

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?

The input schema already provides descriptions for all 7 parameters, achieving 100% coverage, so the baseline is 3. The tool description does not add parameter-specific guidance beyond the schema, but the overall purpose helps infer how parameters like 'toNumber' and 'fromNumber' are used.

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 uses the specific verb 'LOG' and names the resource 'a text message that was already sent by your registered third-party SMS system.' It clearly distinguishes from sending SMS by explicitly stating 'does NOT actually deliver an SMS' and from template tools like createTextMessageTemplate by focusing on recording an actual message.

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 clearly defines when to use this tool: to log an already-sent SMS from a third-party system. It explicitly states what it does not do ('does NOT actually deliver an SMS'), implying not to use it for sending. It does not name specific alternative tools, but the context is sufficient to guide selection among siblings like createCall or createNote.

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