Subscribe to Incoming SMS

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

Discloses WebSocket subscription, push notifications with format, internal ring buffer (100), and idempotent behavior. Annotations already indicate idempotency and non-destructive, but description adds rich context beyond annotations.

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?

Four sentences covering purpose, mechanism, parameter, and idempotency. No redundancy, every sentence adds value.

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 one optional parameter, no output schema, and annotations covering safety, the description is complete. Explains streaming, notification format, buffer, and lifecycle without missing critical details.

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?

Single parameter sim_id is fully described in the schema (100% coverage). Description only restates 'filter to a single SIM,' adding no new semantics beyond schema.

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?

Description clearly states 'Open (or reuse) a WebSocket subscription that streams new SMS for the authenticated user.' It specifies incoming SMS, streaming, WebSocket, and distinguishes from sibling tools like get_sim_messages (batch query) and wait_for_next_sms (polling).

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?

Description explains filtering via sim_id and idempotency, implying use for streaming. However, it does not explicitly mention when to avoid or alternatives, though sibling context helps.

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