mercury_list_credit_statements

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

Goes well past the readOnlyHint/openWorldHint annotations by disclosing the v1→v2 endpoint 404 behavior, the sign-convention change for statements after 2026-06-15, and the critical operational caveat that downloadUrl is short-lived. These are non-obvious traits an agent could not get from structured fields.

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-loads the core action, then uses labeled USE WHEN / DO NOT USE / RETURNS blocks so an agent can scan to the needed section. The changelog sentence is unusual in length but earns its place by preventing misread amounts.

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?

No output schema exists, so the description supplies the return shape itself, including the statement fields and downloadUrl. Combined with the endpoint caveat and sibling routing, an agent has everything needed to call this correctly on the first attempt.

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 single accountId parameter is already documented as coming from mercury_list_credit_accounts. The description reinforces that it must be an IO Credit account, but adds no format or sourcing detail beyond the schema, so baseline 3 applies.

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 ("list monthly statements for a Mercury IO Credit card account") and immediately distinguishes itself from mercury_list_statements and mercury_list_treasury_statements. An agent can identify the correct tool without opening any schema.

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 USE WHEN block names the concrete scenarios (accounting, audit, CPA) and the DO NOT USE block names the two sibling alternatives plus the excluded resource types. Nothing about tool selection is left to inference.

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