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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so safety is covered. The description adds that output includes "what the checker found," which is genuinely useful, but "paint pieces for real" reads like a mutation and creates doubt about whether this writes or merely renders. For a rendering/inspection tool that ambiguity is a real cost.

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?

Two short sentences with no filler, so it is not verbose. However, the brevity comes from under-specification rather than efficiency; the front-loaded clause "Paint pieces for real" is the least informative part and would be better replaced with a plain statement of what is rendered.

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?

With no output schema, the description must explain what comes back, and it only alludes to "what the checker found" without saying what a checker is or what the findings look like. For a tool an agent would use to verify rendered output, that leaves the return contract and the meaning of "pieces" unexplained.

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 50%: `document_id` is documented in the schema but `names` is not. The description compensates partially by explaining that omitting `names` targets all pieces, which is the key semantic. It still never says what a "name" identifies or what form it takes, so it adds meaning without fully closing the 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 says "Paint pieces for real and see them, with what the checker found," which is figurative rather than a concrete verb+resource statement. It gestures at pieces and a checker but never states plainly that it renders pieces and reports validation findings. Nothing distinguishes it from ads_read_piece, ads_list_pieces, or ads_write_piece.

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 only guidance is the parameter default ("Without `names`, all of them"), which is invocation behavior, not when-to-use. There is no statement of when to call this instead of ads_read_piece or ads_list_pieces, and no prerequisites or exclusions.

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