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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description still adds real behavior: default sort order (newest first), default filtering of archived items, and the output-rendering contract that `[[diagram:ID]]` alone on a line becomes a clickable card. Minor gap: no pagination or result-count behavior mentioned.

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 sentences, front-loaded with the core action and scope, followed by filtering and routing. No redundancy; the citation-format sentence earns its place because it governs how the agent must emit output.

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 carries the return-shape burden and does so adequately — it states what is listed, in what order, what is excluded by default, and how to retrieve per-item detail. Safety is covered by annotations, so nothing material is missing for correct invocation.

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 100%, so all three parameters (q, workspace, includeArchived) are already documented in structured data; baseline is 3. The description restates q's title-matching and includeArchived's archived-reveal behavior without adding format or syntax beyond the 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?

States a specific verb and resource ('Lists the workspace's Napkin diagrams') and defines the artifact inline as 'interactive flowcharts — processes, decision trees, system maps', which separates it from the sibling napkin_boards_list (sketches) without opening either schema. 'Newest first' adds ordering scope.

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 conditionals: archived hidden unless `includeArchived`, `q` narrows by title, and routes to napkin_diagrams_get for a single diagram's mermaid source. It also states the exclusion — never cite a diagram as [[board:ID]] because boards are sketches — which is a genuine when-not rule.

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