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

The description goes well beyond the annotations by disclosing error behavior ('never raises a protocol error — it returns {"error": ...}'), the matching criteria in detail, and the read-only/idempotent nature. It also explains the tax implication ('so basis and holding period move with the coins instead of being treated as a sale'), giving the agent important behavioral context.

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?

Despite being long, every sentence earns its place: purpose, example, matching criteria, usage timing, exclusions, error behavior, and idempotency. The information is dense but logically ordered and front-loaded with the core purpose, making it easy for an agent to extract the key 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?

The description is complete for an agent to call this tool correctly: it explains the input shape, output shape, matching rules, error handling, usage order relative to siblings, and what scenarios are out of scope. Combined with the rich input schema and annotations, nothing critical is missing.

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 100%, so the baseline is 3. The description adds extra meaning by explaining tolerance_pct in context ('quantity within tolerance_pct of the amount sent net of the fee') and providing a typical input example with window_minutes. Ledger remains described only as 'canonical rows' in the schema, but the example and matching logic give enough practical context.

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: 'Pair withdrawals with the deposits that received them between your own accounts.' This clearly distinguishes match_transfers from sibling tools like build_lots and parse_transactions by stating exactly what operation it performs and on what data.

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 explicitly states when to use the tool ('Use before build_lots'), what it is not for ('Not for transfers to third parties'), and what to do instead ('those stay unmatched and should be typed gift_out or sell'). This provides clear routing guidance with no ambiguity.

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