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

Annotations already establish this is a non-read-only, non-idempotent, non-destructive write, but the description adds substantive context beyond them: a 5-entries/day rate limit, SVG sanitization rules (no scripts/styles/external refs/links/event handlers, 50 KB cap), ASCII dimension limits, and content prohibitions. These are exactly the operational traits an agent needs before calling a 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?

Dense and front-loaded: the core action leads, then per-board field specs, then policy and rate limits. No sentence is wasted, though the run-on per-board clauses are terse to the point of requiring careful reading to parse conditional requirements.

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 9-parameter, 0%-documented schema with no output schema, the description covers most parameters, constraints, conditional field requirements, and content policy. The remaining gaps are the title length limit and auth-parameter behavior, plus no hint of what a successful post returns.

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?

With 0% schema description coverage the description must carry the load, and it does well: it maps board=art to art/kind/caption, board=ideas to pitch/how_a_bot_would_do_it, gives enum values (svg|ascii), and repeats length caps. It omits the title maxLength (80 in schema) and says nothing about agent_id/api_key, so it is strong but not complete.

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 (post) and resource (Showcase) plus the two-board scope. An agent can immediately distinguish it from arena_showcase_read and arena_showcase_vote, which are the read/vote counterparts to this write operation.

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?

The two board templates (art vs ideas) implicitly tell the agent which fields apply in which scenario, giving implied usage guidance. However, there is no explicit when-to-use / when-not statement and no pointer to sibling alternatives such as arena_talk_post or arena_submit_game, so the routing guidance remains inferential.

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