Get Credit Balance

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

Goes well beyond the annotations (readOnly/idempotent/openWorld) by disclosing the lag window versus in-flight metered operations, the authoritative 402 signal, that negative ledger balances are clamped to 0, and the source and null semantics of next_grant_at.

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-loads the core purpose and follows with behavioral caveats, then a permission block. The permission section is somewhat templated but relevant, and no sentence is wasted.

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 read-only balance tool with no output schema, the description covers interpretation of the value, edge cases (negative balances, null next_grant_at), and auth requirements, leaving nothing material an agent needs to call it correctly.

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 the baseline is 3, but the description adds meaningful semantics by clarifying that the account is always derived from the authenticated token and that the endpoint accepts no account identifier, reinforcing what the 'account' parameter actually selects.

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 ('Retrieves the current account's available credit balance') plus the secondary output ('expected next recurring credit grant time'). It is unambiguously distinct from siblings like get_account_usage or get_account_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?

Gives clear interpretive context: the balance is a near-real-time hint that may lag, and a 402 is authoritative when deciding whether more credits are required. It does not explicitly name an alternative tool to use instead, but the when-to-trust guidance is strong.

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