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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered; the description adds real behavioral context by listing the three situations in which the check is refused and clarifying the credit is tied to the first deposit. It stops short of saying what the success payload contains (e.g., credit amount or currency).

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?

Two tight sentences, front-loaded with the purpose, then refusals and the companion call. Minor ambiguity in the phrase 'over', which reads like a truncation of 'expired' and slightly blurs the refusal condition.

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 two-parameter read-only check with no output schema and full schema coverage, the description supplies purpose, refusal conditions, and the follow-on call. A hint about what the result reveals (credit amount vs. mere validity) would close the remaining gap.

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 'code' (case-insensitive, length bounds) and 'org' (default first org) are already documented. The description adds nothing parameter-specific, which is acceptable given the schema does the heavy lifting.

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 ('Check a promo code') plus the outcome being determined ('what it adds to this workspace's first deposit'), which goes beyond the title. It is clearly not the deposit action itself, but does not explicitly contrast with the other billing siblings (balance, ledger, pricing).

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?

Gives explicit preconditions and refusal cases (unknown/over code, workspace that already has credits) and names the companion call 'cloud.billing.deposit --code'. No competing alternative exists to exclude, so this is close to complete guidance.

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