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

Annotations already declare readOnly, idempotent, and non-destructive behavior, and the description adds substantial context beyond that: the snapshot-vs-live semantics, the sync anchor meaning of updatedAt, credit-specific error warnings, and the degradation fallback with realtime:false. This fully discloses behavioral traits an agent would otherwise have to infer or discover at runtime.

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 but every sentence earns its place: purpose, freshness caveat, sync guidance, parameter constraint, error modes, degradation behavior, and response shape. It is front-loaded with the core action and scopes successive caveats logically, making it easy for an agent to extract the essential facts quickly.

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?

Given the tool has a single parameter, no output schema, and no nested structure, the description covers all needed ground: it states the response shape, error array format, edge-case warnings, and the relationship to force_sync. The agent has enough information to decide when to call it, what parameters to pass, and what to expect in return.

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?

The schema has a single required account_ids array of strings with no descriptions (0% coverage), so the description carries the burden. It adds the key constraint 'Pass account_ids as an array (1–50)' and clarifies it works per account ID. It could have explained where the IDs come from (e.g., from openfinance_list_accounts) or their format, but the provided guidance is sufficient for safe 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 ('Returns') and resource ('latest available balance per account id'), and makes the tool's scope explicit by naming the exact endpoint. It clearly distinguishes itself from siblings like openfinance_list_accounts (which lists accounts) and openfinance_force_sync (which syncs data), so an agent can pick it without guessing.

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 gives explicit when-to-use guidance: use it for the freshest balance the provider can serve, and if the balance is stale or disagrees with transactions, run openfinance_force_sync then re-read. It also tells the agent when not to expect live data and how to handle credit-account and provider-outage edge cases, which effectively routes to alternatives when needed.

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