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

With no annotations provided, the description carries the burden and does notable work: it declares the operator-only restriction and "requires proof" auth requirement, discloses that renaming the code preserves existing patron redemption rows, and explains that tool_ids replaces (not merges) the binding. It omits failure modes, what happens to unspecified fields' side effects, and rate/permission specifics.

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?

Purpose is front-loaded in the first sentence, then the paragraph is ordered from general patch semantics to the edge cases an agent is most likely to get wrong (null clearing, rename safety, binding replacement). It is dense and slightly awkwardly line-broken, but no sentence is 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?

An output schema exists, so return values need no explanation, and the description supplies the auth requirement, the partial-update contract, and the null-clearing convention the schema cannot express. Remaining gaps are the undocumented dpop_token and date/percentage parameters, which are relatively self-evident from their names.

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% across 11 parameters, so the description must compensate, and it does for the counterintuitive ones: it explains the clear_uses_per_patron/clear_total_uses flags that exist because nullable fields default to null, plus full semantics for tool_ids ("*" for all paid tools, [] to unbind). dpop_token, valid_from, valid_until, discount_percent and the raw cap fields remain undocumented in both description and schema.

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") that cleanly separates this tool from weather_mint_coupon, weather_delete_coupon, weather_list_coupons and weather_forget_coupon. An agent can route to it without reading the sibling schemas.

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 invocation contract clearly ("Pass only the fields you want to change"), so the agent knows this is a partial patch rather than a full replace, and it explains the clear_* escape hatch for setting caps to unlimited. It never names an alternative tool or says when patching is preferable to minting/deleting, so it stops short of full when/when-not guidance.

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