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

With no annotations, the description carries the full burden and does so well: it discloses the auth constraint ('RESTRICTED to operator — requires proof'), the NULL-vs-clear-flag semantics, that renaming the code preserves existing patron redemption rows, and that tool_ids replaces (not appends to) the binding. It does not cover failure modes or error behavior, but the disclosure depth is well above average for an unannotated mutation tool.

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 with the core action, then organized into short paragraphs each handling a distinct concern (patch semantics, NULL clearing, rename safety, binding replacement, auth). Dense but every clause earns its place; no filler.

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?

Given 11 parameters, an existing output schema, and no annotations, the description supplies what structured fields cannot: patch semantics, NULL-clearing convention, rename side effects, binding replacement rules, and the operator/proof requirement. An agent has enough to invoke it correctly; only discrete edge behavior is left unstated.

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 0%, so the description must compensate — and it targets the genuinely ambiguous parameters: the clear_uses_per_patron/clear_total_uses flags, the tool_ids replacement semantics with the '*' and '[]' sentinels, and rename behavior on name. Simpler fields (valid_from, valid_until, discount_percent, dpop_token) are left to their self-describing names, a minor residual gap.

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+resource ('Patch a coupon's editable fields'), clearly distinguishing this from siblings like mint_coupon, delete_coupon, and list_coupons. It stops short of explicitly naming which sibling to prefer in a given situation, but the operation itself is unambiguous.

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?

'Pass only the fields you want to change' conveys the partial-update contract, which is genuine usage guidance. However, it never states when to reach for this tool versus delete_coupon/forget_coupon/mint_coupon, nor any prerequisites beyond the operator restriction, leaving selection context implied rather than spelled out.

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