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

Annotations already indicate this is a mutation (readOnlyHint=false). The description adds the effect on success (owner verified, agents can message, platform numbers connectable), which is useful context. However, it does not mention failure behavior, idempotency (already false), or error handling beyond that. It adds some value but is not comprehensive.

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?

Two sentences with no waste. The first sentence states the action and source, the second gives the consequence. All essential information is front-loaded, making it quick for an agent to parse.

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 simple verification confirm, the description provides the flow context (paired with start_owner_phone_verification) and the outcome. It does not cover failure scenarios or return format, but this is not critical for a basic confirmation tool. The lack of an output schema is not a major gap here.

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 all parameters are documented in the schema. The description adds minimal extra meaning—it mentions the code was received from start_owner_phone_verification, but this is already implied by the schema's 'from the WhatsApp message.' With complete schema coverage, baseline 3 is appropriate.

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 clearly states the action ('Confirm the 6-digit code') and the resource (owner phone verification from start_owner_phone_verification). It also explains the outcome, distinguishing it from siblings like start_owner_phone_verification by referencing that paired flow.

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 explicitly ties the tool to start_owner_phone_verification, indicating it should be used after that flow and after receiving the code. It does not explicitly state exclusions or alternatives, but the context is clear enough for an agent to know when to use it.

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