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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so safety is covered. The description adds genuinely non-obvious behavior: the account set is fixed, some accounts may exist in use without a mapping, and the tool will not invent a mapping for those — the agent must escalate instead. It does not describe the shape of the returned map, but that gap is modest.

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?

Two short sentences, the usage rule front-loaded, and the escalation constraint stated in the same breath. Nothing is repeated from the title or annotations.

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?

For a no-param, no-output-schema read with full annotation coverage, the description supplies the two things an agent actually needs: when to call it and what to do about unmapped accounts. It could say slightly more about what the returned mapping looks like, but that is the only real gap.

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 tool takes zero parameters, so there is no parameter semantics to explain; baseline for a no-param tool applies. The description correctly implies a whole-map read with no filtering.

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 enumerates exactly what the map contains: the fixed derivation accounts, which of them the books actually use, and their ledger-of-record names. That is a specific resource with concrete contents, though it is phrased as a noun list rather than a verb, and it never names a sibling (e.g. bridge_map_account, bridge_exports) to distinguish itself from.

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?

"Read this before any export" gives an explicit precondition for use, and the second sentence gives a clear rule for the ambiguous case (in-use but unmapped accounts get escalated to a person/accountant, not guessed). It stops short of naming the export sibling or saying when the tool is unnecessary.

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