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

Goes well beyond the annotations by disclosing code lifetime (10 minutes), attempt budget (five), a security property ('The provider code is never returned'), and a concrete rate limit with its replenishment rule. Annotations only say non-read-only, non-idempotent, non-destructive; the description adds the operational constraints an agent needs to avoid failing calls.

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 the core action, then the code lifecycle, then the rate limit — each clause carries distinct operational information with no filler or repetition.

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 single-parameter, non-idempotent side-effecting tool with annotations and no output schema, the description covers timing, retry limits, and the security-relevant fact that the code is not returned. The remaining gap is that it never explains the optional key_name parameter or points to signup_verify as the completion step, which an agent would need to finish the flow.

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 0%, so the description carries the burden, and it only indirectly characterizes the email parameter via 'per address' and the inbox concept. The optional key_name parameter (max 60 chars) is never mentioned anywhere, leaving its purpose entirely undocumented.

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 ('Creates an account') and adds a second mode ('recovers access through an API-readable inbox'), which tells an agent this initiates an email-code flow rather than a password login. It does not name or differentiate itself from the obvious sibling signup_verify, so the boundary of the flow is left implicit.

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?

Usage is implied rather than stated: 'creates an account or recovers access' tells the agent the two situations this covers, but there is no explicit instruction on when to call this versus account, signup_verify, or key_create, and no statement of prerequisites. The rate-limit and expiration facts indirectly convey that this is a first step in a two-step flow, but the agent must infer the handoff to signup_verify.

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