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

Annotations already declare readOnly, idempotent and non-destructive behavior, so the safety profile is covered. The description adds genuinely new behavioral context: it maps to GET /v1/balance and explicitly states the API key is NOT returned, which is security-relevant output information absent from the annotations and schema.

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, front-loaded sentences with zero filler. The primary capability is stated first, followed by the REST equivalent and the explicit exclusion.

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 simple read-only wallet query with rich annotations and full parameter documentation, the description supplies what is missing (returned fields, REST mapping, no secret leakage). Only the absence of any error/authentication-failure behavior keeps this from a 5.

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 100%: the single api_key parameter is fully documented, including the Bearer fallback and the BOTSUPPLY_API_KEY env var. The description adds nothing about parameters, so the baseline 3 applies.

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?

The description names a specific verb and resource (returns the wallet id and prepaid credit balance), which clearly distinguishes it from siblings like create_checkout or purchase. It stops short of explicitly contrasting itself with any sibling tool, so it lands at 4 rather than 5.

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?

There is no when-to-use or when-not-to-use guidance and no alternatives are named. The agent can infer this is the tool for checking available credit, but nothing tells it how balance checking relates to purchase or open_wallet flows.

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