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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, covering safety. The description adds meaningful behavioral context: balance is a snapshot anchored to the last upstream sync, not a live read; certain errors are returned as structured `warning` rows rather than thrown exceptions; and specific error codes like BALANCE_FETCH_ERROR and BALANCE_CONSENT_ERROR are explained. This goes beyond the annotations and helps the agent interpret unusual responses correctly.

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 dense and detailed, and the core purpose is front-loaded. Every sentence adds useful information about freshness, error handling, or usage guidance. It is longer than a minimal description, but the length is justified given the nuanced sync and error behavior, and it remains well-structured with clear cause/effect statements.

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 single-parameter read tool, the description covers the most important operational context: staleness semantics, the relationship to force_sync, the array constraint, and credit-account error handling. There is no output schema, so the mention of `updateDateTime`/`updatedAt` and the structured `warning` helps set expectations. It does not describe pagination, but with a 1–50 array limit that is less critical. Overall it is adequately complete for an agent to call this tool correctly in most real scenarios.

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 0%, so the description must carry parameter meaning. It does: it explains that `account_ids` should be passed as an array of 1–50 items. It does not enumerate all array element semantics beyond that, but for a single-parameter tool this is sufficient and directly compensates for the schema's lack of description.

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 clearly states it returns the latest available balance per account id, specifies the exact endpoint (GET /accounts/:id/balance), and distinguishes itself from related list operations. It gives the agent a precise verb-resource pairing (get account balance) that is unambiguous even among many openfinance siblings.

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 explains when to use this tool, when the data may be stale, and names the alternative (openfinance_force_sync) to run first if fresher data is needed. It also addresses error conditions and consent failures, so the agent has clear routing and remediation guidance.

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