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

Annotations already declare a non-read-only, open-world, non-destructive write, and the description adds real context: the account is free, email is optional with different downstream consequences, and terms acceptance is mandatory. It does not mention that repeat calls are non-idempotent (each call would likely create a new account), which is the one behavioral trait left implicit.

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?

Front-loaded with the purpose, then the branching behavior and prerequisites; nearly every sentence earns its place. The 'No inbox?' sentence with its nested parenthetical is slightly dense but still readable.

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 no output schema, the description does the needed work by telling the agent what the response contains (API key and referral code) in the no-email path and that the email path defers to partner_confirm. What partner_confirm ultimately returns is left unstated, a minor gap for a multi-step 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 coverage is 100%, so baseline is 3, but the description adds meaning beyond the schema: it clarifies that omitting email is a supported path with its own return payload, and that the agent's operator is the member and payee (relevant to the 'kind' choice). That is genuine added semantics rather than restatement.

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 ('Create a free partner account') plus the business outcome (commission share). This clearly separates it from siblings like partner_add_email, partner_confirm, partner_signin, and partner_stats.

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?

Explicitly routes the two flows: with an email, a one-time code goes to partner_confirm; without an email, the response carries the API key and referral code directly. It also names partner_add_email as the prerequisite for payouts and states accept_terms must be true — when-to-use and alternatives are fully covered.

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