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

The readOnlyHint annotation already covers the safety profile, and the description layers on genuinely non-obvious behavior: historical_import with status 'running' or 'pending' means figures will keep rising and must not be presented as final, and clearing_balances values are explicitly flagged as informational and NOT errors, with the Stripe-only settlement_in_transit accumulation explained. It also warns that a non-zero unreviewed_event_count makes the P&L incomplete. This materially changes how an agent should phrase its answer.

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?

Long, but every sentence earns its place: core composition first, then two clarification clauses that prevent misreading (clearing balances vs errors, in-flight import finality), then routing guidance. The most important operational caveat, 'START HERE... only fall back', is placed prominently and the structure moves from what → caveats → when. No 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?

The output schema answers return-value shape, while the description supplies the interpretation layer: what to call out, what to flag as non-final, and what to do next when data is incomplete. Combined with the annotations and sibling list, an agent has everything needed to invoke it correctly and present results responsibly.

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 description coverage is 100% and the org_id schema text already explains defaulting, omission, and rejection on mismatch, so the baseline of 3 applies. The tool description adds no parameter-level detail, but none is needed given the schema carries the full burden for the single optional parameter.

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?

Opens with a specific verb+resource phrase, 'One-call financial snapshot of an organisation', then enumerates exactly what is included: current-month P&L, connected-provider balances, unreviewed_event_count, ledger_sync health, clearing balances, and historical import. It disambiguates against siblings by noting the P&L and balance shapes match get_pnl_report and get_account_balance, and names get_unreviewed_events as the follow-up. There is no ambiguity about what this tool is for.

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?

Gives an explicit routing rule: 'START HERE for any briefing, health check, or "how are the finances" question; only fall back to the individual tools when you need a different period, specific providers, or the review queue contents.' It also states the follow-up condition ('If unreviewed_event_count is non-zero... follow up with get_unreviewed_events'). The when-to-use and when-not-to-use logic is fully spelled out.

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