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

Annotations declare readOnlyHint=false, idempotentHint=false and destructiveHint=false; the description explains WHY the call is not idempotent ('a right code works once'), documents a lockout behavior ('5 wrong codes lock it'), and notes billing impact ('Uses no allowance'). These are behavioral traits well beyond what the annotations convey.

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?

Dense and front-loaded: usage, parameter selection, then return values. The status enumeration is long but each term is load-bearing; phrasing is slightly telegraphic in places ('Give to ... or id, and code').

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, yet the description fully enumerates the return shape (valid boolean plus status values) and covers the failure and lockout paths. Nothing an agent needs to call or interpret this tool is missing.

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%, so the baseline is 3, but the description adds real meaning: `to` resolves to the newest code for that address and `id` is the identifier from verify_start, which the schema descriptions only gesture at.

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?

Names a specific verb and resource ('Check a code from verify_start') and identifies the sibling that produces the input, so the agent can place it in the flow without opening the schema. It is clearly distinct from verify_start and from unrelated siblings like check_email or validate_email.

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?

States the precondition (a code from verify_start) and clarifies the `to` mode ('checks the newest code sent there') versus supplying `id`. It gives no explicit when-not guidance, but the entry point is unambiguous.

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