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

With no annotations, the description carries the burden and does disclose key traits: it blocks/waits, it is scoped to your own numbers, and 'each code is returned once' (single-consumption semantics). It omits what happens on timeout (error vs empty return) and any auth/rate-limit notes, which is the only gap.

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?

Three short sentences, front-loaded with what it does and immediately followed by the trigger condition. No wasted words; the one-time-return caveat is placed last, which is appropriate.

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?

No output schema exists, but the description states the tool returns the code, so the agent knows what to expect. Combined with fully documented parameters, the only missing piece is timeout/failure behavior, which a short additional clause would cover.

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 api_key, service, number_id, and timeout_seconds are already documented in the schema. The description reinforces the number scoping but adds no syntax or format detail beyond the schema, 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?

States a specific verb and resource ('Wait for a verification code (OTP) ... and return it'), which clearly distinguishes it from list-style reads like read_text_messages. It doesn't name a sibling for contrast, so it stops just short of a 5.

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?

Gives an explicit trigger condition: 'Call this right after a site says it sent you a code.' That's clear timing guidance, but it doesn't mention when NOT to use it (e.g., to read arbitrary messages use read_text_messages instead).

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