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

Beyond annotations, the description reveals critical behavioral traits: balance is a snapshot anchored to the last upstream sync, not a live read; CREDIT accounts may return specific errors (BALANCE_FETCH_ERROR, BALANCE_CONSENT_ERROR) as warnings instead of throwing; and upstream unavailability degrades rows to last-synced data with realtime:false and a warning. It also details the response envelope, giving the agent a full understanding of expected behavior.

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, staleness nuance, refresh guidance, parameter constraint, error modes, degradation behavior, and response shape. It is front-loaded with the main purpose, and the logical flow moves from normal behavior to edge cases to error handling without extraneous content.

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's complexity, the description covers everything an agent needs: snapshot semantics, when to force sync, credit-specific errors, degraded fallback behavior, and the response structure. Without an output schema, it still provides enough shape ('{ results: [...], errors: [{ id, status, message }] }') to let the agent parse results correctly. No missing critical information was found.

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 only declares account_ids as an array of strings with zero description coverage, so the description carries the burden. It adds the crucial constraint 'Pass account_ids as an array (1–50)', which enforces cardinality bounds not present in the schema. It could have explained the ID format or source, but for a single parameter the added semantics are meaningful.

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 even cites the exact endpoint (GET /accounts/:id/balance). It clearly distinguishes this from sibling tools by focusing solely on account balance and referencing related tools like openfinance_list_transactions and openfinance_force_sync without ambiguity.

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 the tool and when to take an alternative action: 'If a movement that just happened is not reflected yet, or the balance disagrees with the sum of openfinance_list_transactions, run openfinance_force_sync to pull fresh data and then re-read.' It also explains handling for CREDIT errors and degraded responses, which helps agents decide how to interpret results.

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