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

Annotations declare readOnlyHint, idempotentHint, and destructiveHint, and the description adds substantial nuance on top: the balance is snapshot-based on the last upstream sync, errors may be returned as non-throwing structured warnings, and rows can degrade to a stale balance with realtime:false. No contradiction with 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 long, but nearly every sentence carries an operational consequence: freshness semantics, sync remedy, error modes, degradation behavior, and response shape. It is dense rather than padded, with the core purpose front-loaded.

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?

With no output schema, the description takes on the burden of explaining the response shape ({ results, errors }) and covers degraded rows, warning fields, and provider-specific errors. An agent has enough detail to call the tool correctly and interpret its output.

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%, but the description fully compensates for the only parameter: it tells the agent to pass account_ids as an array, limits it to 1–50 items, and clarifies that results are per account id. This is meaning the schema alone does not provide.

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 (GET /accounts/:id/balance).' It clearly identifies the tool's scope and distinguishes it from sibling tools like openfinance_force_sync and openfinance_list_transactions without needing to read their schemas.

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 states when to use the tool and when to use an alternative: if a recent movement is missing or the balance disagrees with transactions, the agent is told to run openfinance_force_sync and then re-read. This is direct, actionable routing guidance.

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