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

Adds real behavior beyond the annotations: per-line cost, zero cost when nothing matches, and a failure mode (locked month → listed under skipped with a reason). It does not address whether re-running re-books previously booked lines, which matters given idempotentHint=false.

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?

Front-loaded and mostly tight, but the cost is stated twice in nearly identical words ('$0.02 per line booked' and 'Costs $0.02 per bank line booked; nothing if none are found'), wasting a full clause.

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?

Covers preconditions, scope, cost, and the skipped outcome, which is strong for a mutation tool with no output schema. It does not describe what a successful result returns (e.g., count booked), leaving the agent to infer the shape.

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 50% (limit undocumented in the schema), but the description covers both: 'up to limit' and 'on one bank account or all' clarify that bank_account is optional and scoping-only. It still doesn't state what limit bounds (lines booked vs. lines scanned).

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?

States a specific verb and resource ('Book every new bank line a rule matches') plus scope details: oldest-first ordering, first-matching-rule semantics, limit, and one-or-all bank accounts. It is clearly distinct from books_match_bank_lines, which it names as the fallback for unmatched lines.

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?

Explicit sequencing ('Run it after books_import_bank') and explicit routing for the alternative ('Lines no rule matches wait for books_match_bank_lines'). The agent knows both when to call this and when not to.

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