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

The annotations already mark this as read-only and idempotent, but the description adds essential behavioral context: the balance is a snapshot tied to the last upstream sync, not a live read, and errors can be returned as structured warnings rather than thrown exceptions. It also names specific error types and degradation conditions, which goes well beyond the annotations.

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?

The description is front-loaded with the core purpose and endpoint, then systematically covers limitations, corrective actions, parameter usage, and error handling. Every sentence adds useful information; there is no filler or redundancy.

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?

Despite having no output schema, the description adequately explains the return context: rows contain updateDateTime/updatedAt, balance is per account id, and error rows include a structured warning. It also covers the relevant upstream/connector failure modes, making the tool safe and predictable for an agent to invoke and interpret.

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 0%, so the description must compensate. It does add key meaning: 'Pass `account_ids` as an array (1–50)' provides a required constraint not in the schema. However, it does not explicitly define where account_ids come from or how they are structured beyond being an array, leaving a small gap.

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 states a specific verb and resource: 'Returns the latest available balance per account id' and cites the exact endpoint 'GET /accounts/:id/balance'. It clearly differentiates this from sibling tools like openfinance_list_accounts or openfinance_list_transactions by focusing on balance retrieval.

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?

The description explicitly tells the agent when to use it, when the result may be stale, and what to do instead: if the balance is stale or disagrees with openfinance_list_transactions, run openfinance_force_sync and re-read. It also covers the reconnect remedy for BALANCE_CONSENT_ERROR, giving clear actionable guidance.

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