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

Annotations leave real gaps (no auth, rate-limit, or idempotency detail), and the description fills them: authentication not required, rate-limited per email and per client, 0-credit cost, and the crucial fact that no key exists until the owner clicks the sign-in link. This is behavior an agent cannot infer from readOnlyHint/openWorldHint.

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 purpose and mechanism, and nearly every sentence carries operational value (token flow, auth, rate limits, cost). The closing 'It is not investment advice' is boilerplate noise that doesn't help invocation, keeping it from a 5.

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 correctly covers return values (a `request_token` on first call, the key on the confirmed repeat call), plus auth, rate limits, and cost. An agent has everything needed to call this correctly across both phases.

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 both parameters are documented; the description adds sequencing semantics the schema cannot express — that `request_token` comes from the first call and is only sent after owner confirmation, and that `email` is the key owner. That is genuine added meaning above the baseline.

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 (request a RentSeek API key) and immediately scopes the outcome (100 credits, free). The two-phase mechanism (sign-in link, no key until clicked, token-then-key) makes it unmistakably distinct from the read-only siblings like get_company_dossier and list_available_tickers.

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?

Spells out the exact call sequence: first call with `email` returns a `request_token`; repeat call with `email` + `request_token` after the owner confirms returns the key once. This is effectively when-to-use guidance. It doesn't discuss explicit alternatives, but there is no competing sibling for key issuance.

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