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

Annotations only cover the safe-read profile; the description adds substantially more: no mutation occurs, the draft is served from a temporary cache, the previewUrl is anonymous, it expires after previewExpiresInSeconds, and re-calling renews it. It also discloses client-dependent behavior (renders a widget in UI clients, returns a URL elsewhere), which no structured field conveys.

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 core (what it previews, when to call, when not to) is front-loaded and the sizing is justified by the amount of behavioral detail. A few clauses are redundant, notably restating 'the Riddle as it looks right now' and the trailing reference_get pointer, which mildly dilutes an otherwise dense paragraph.

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?

Return values are covered by an output schema, so the description is free of that burden, and it still explains previewUrl semantics and expiry that the agent needs to act on. Client-rendering divergence, publication state fields, and renewal behavior are all covered, so nothing an agent needs to call this correctly is missing.

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?

There is a single required parameter with 100% schema description coverage, so the schema already does the work and the baseline is 3. The description doesn't add format, sourcing, or lookup guidance for the UUID beyond referring to 'a Riddle', leaving nothing extra but nothing missing either.

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 concrete verb+resource ('Shows the user the current DRAFT of a Riddle as a playable preview') and immediately scopes it to the draft-vs-live distinction, which separates it from riddle_get and riddle_publish. An agent can tell exactly what this does without opening the 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?

Gives explicit triggers ('after riddle_builder_create or riddle_builder_update whenever the user wants to see the result') and an explicit anti-pattern ('do not call it on every edit of a multi-step build, once at the end is enough'). It also notes the equivalence right after riddle_publish, so the agent knows when calling is pointless.

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