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

Beyond the annotations (readOnlyHint=true, idempotentHint=true), the description discloses critical behavior: the balance is a snapshot anchored to the last upstream sync, not a live read; credit accounts may produce structured warnings instead of throwing; and upstream 5xx or non-Open Finance connectors cause graceful degradation. This is exactly the kind of context annotations cannot capture.

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 dense and every section serves a purpose: freshness caveat, sync escalation, array constraints, error semantics, and degradation conditions. It is not as front-loaded as it could be, but the structure is logical and no sentence is filler.

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 partially compensates by mentioning rows, updateDateTime/updatedAt, and structured warnings, but it does not fully describe the response shape or what fields an agent can expect in the balance payload. Given the tool's complexity and error modes, this is a minor gap rather than a blocking one.

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 carry parameter meaning, and largely does: it specifies account_ids, explains it must be passed as an array, and imposes the 1–50 count constraint. It does not explicitly say that the IDs come from openfinance_list_accounts, but the first sentence's 'per account id' plus the array requirement offers enough semantic grounding for an agent to invoke it correctly.

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 ('Returns') and resource ('latest available balance per account id'), and includes the exact endpoint. It is immediately distinguishable from siblings like openfinance_list_accounts, which lists accounts rather than balances, and openfinance_list_transactions, which returns movements.

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 guidance on when to use this tool and what to do if the data is stale: it instructs the agent to run openfinance_force_sync and re-read when the balance disagrees with openfinance_list_transactions or when recent movements are missing. It also names openfinance_list_transactions as a related but distinct alternative.

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