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

Discloses the key non-obvious behavioral trait beyond annotations: by default the expiration is removed so the coupon becomes valid with no deadline, and expires_at must be supplied to set a new one. This matters because annotations only say idempotent/non-destructive/not read-only. It does not cover failure behavior (unknown id/code) or what an already-active coupon does.

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?

Three short sentences, front-loaded with what the tool does, then the default/override behavior, then identification. No filler or redundancy.

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?

Covers purpose, source of coupons, default expiry behavior, override semantics and identification; an output schema exists so return values need no explanation. Missing only edge-case behavior (missing/unknown identifier, coupon already active), which is a modest gap for a mutation tool.

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 100% and the schema already documents the id/code alternative and the expires_at default and format notes, so the description largely restates structured data. It adds only the framing that id/code are mutually alternative identifiers, which is already implied by the schema text.

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 (reactivate an expired/inactive coupon) and scopes it to coupons surfaced by list_coupons with status="expired", which cleanly separates it from add_coupon, remove_coupon and list_coupons.

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?

Explicitly ties the tool to the expired-coupon case from list_coupons and explains both identification options (id or code). It does not state what to do instead for non-expired coupons or what happens if neither identifier matches, 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.