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

Annotations already declare this is a non-readonly, non-idempotent, non-destructive, open-world mutation, so the safety profile is covered elsewhere. The description adds only that the code originates with the user; it says nothing about failure behavior (wrong/expired code), retry limits, or what a successful confirmation changes about the account.

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?

One sentence, front-loaded with the action and resource, with zero redundant or hedging text. Nothing could be removed without losing 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?

With only two fully documented parameters and annotations covering safety, the essentials are present. However, for a verification mutation the description omits the request-then-verify workflow and any indication of what result the agent should report back to the user.

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% and the schema descriptions already carry the meaningful guidance ('Ask the user for it; never guess', 'E.164, e.g. +15145550100'). The description restates the code's provenance without adding format, validation, or edge-case detail beyond the 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?

States a specific verb ('Confirm') and resource ('a phone number') plus the required artifact (verification code), which cleanly separates it from request_phone_verification (sends) and get_verified_phone (reads status). It never names those siblings, so the differentiation is inferable rather than explicit.

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 phrase 'the verification code the user received' implies the request_phone_verification prerequisite, but the description never says so directly, nor does it state when not to call this or what to do if no code was ever requested. Usage is implied rather than guided.

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