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

With no annotations, the description carries the full burden and does well: it discloses patch semantics, that renaming survives existing redemption rows (keyed on coupon id), that tool_ids fully replaces the binding, the special ['*'] and [] values, the clear_* flags for NULLing caps, and an operator/proof auth requirement. It stops short of describing rate limits or the return shape, but the behavioral disclosure is strong.

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?

The purpose is front-loaded and the subsequent sentences each carry distinct, useful content (patch semantics, cap clearing, rename safety, tool_ids replacement, auth). It is information-dense but slightly fragmented by the blank-line paragraph breaks.

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 patch tool with an output schema (so returns need not be explained) and 11 params, the description covers the most error-prone aspects: partial updates, special clear flags, binding replacement, rename behavior, and the auth requirement. The main gap is that most scalar params are not individually described.

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 0%, so the description must compensate. It clearly explains the non-obvious parameters (clear_uses_per_patron, clear_total_uses, tool_ids semantics, name/rename behavior), but total_uses, uses_per_patron, valid_from, valid_until, discount_percent, coupon_id, and dpop_token are only implicitly covered by 'editable fields,' leaving roughly half the parameters without added meaning.

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 opening 'Patch a coupon's editable fields' gives a specific verb (patch) and resource, and the later detail about field selection and coupon-code renaming makes the operation unambiguous. It is clearly distinct from siblings like authority_mint_coupon and authority_delete_coupon, though it does not explicitly name those alternatives.

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?

It states the key usage precondition ('RESTRICTED to operator — requires proof') and 'Pass only the fields you want to change,' which tells the agent how to invoke it. However, it never positions the tool against alternatives (mint vs update vs delete), leaving the when-to-use inference to the agent.

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