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

Beyond the read-only/idempotent annotations, the description discloses that the result is a sync-anchored snapshot, that updateDateTime/updatedAt is the sync time rather than a live read, and that certain credit accounts return structured warnings instead of throwing. It also explains upstream 5xx and non-Open-Finance degradation, which annotations alone could not convey.

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 long but information-dense; each sentence adds a distinct caveat or constraint. It front-loads the core behavior before deepening into failure modes. The final 5xx/degradation sentence is slightly awkward and could be clearer, so this is not a perfect 5.

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?

Without an output schema, the description gives crucial runtime context: row-level warnings, error behavior, sync anchoring, and a remediation path via openfinance_force_sync. It leaves the exact response fields (e.g., numeric balance, currency) unspecified, but an agent can still invoke the tool correctly based on this description.

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 carries the burden. It tells the agent that account_ids must be an array and imposes the 1–50 count limit, while also tying the parameter to account ids used elsewhere. It does not specify the exact string format of the IDs, but enough context is provided for correct invocation.

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 opens with a specific verb and resource: 'Returns the latest available balance per account id' and names the API endpoint (GET /accounts/:id/balance). This clearly distinguishes it from sibling tools like openfinance_force_sync and openfinance_list_transactions by focusing on a point-in-time balance read.

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?

It explicitly covers freshness semantics and tells the agent to run openfinance_force_sync and re-read when the balance is stale or disagrees with openfinance_list_transactions. It also sets expectations for credit-account error and consent cases. It does not formally list 'when not to use', but the context is clear and actionable.

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