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

Annotations only declare readOnly/idempotent/no-open-world, so the description must carry the operational burden and does: it says to infer missing details rather than ask the user, states hard limits (3–10 spokes, one level, 1–3 word names, ~12 word details), and explains the builder Edit link for post-hoc adjustment. Most importantly it gives the output-handling rule — always surface the image link because inline chat images usually cannot be saved — which no annotation or schema 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?

Front-loaded with what the diagram is and when to choose it, then limits, then output handling — a sensible priority order. It is dense and nearly every clause carries information, though the list of alternative diagram types and the example-domain list (platform/products, team/stakeholders, etc.) are somewhat expansive for a single tool description.

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 still tells the agent what the artifact is and how to deliver it (image link, editable in builder). Combined with a fully documented 8-parameter schema, an agent has everything needed to call this correctly and hand the result to the user.

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%, so the baseline is 3; the description still adds value by stating the authoring constraints the schema can't express — 3–10 spokes, single level, 1–3 word names, roughly 12-word details. It does not add per-parameter meaning beyond that (e.g. when to set palette vs hubColor), so it sits above baseline but not at the top.

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?

Opens with a specific verb and resource ("Generate a slide-deck-quality hub and spoke diagram") and immediately describes the visual anatomy: a central hub circle, 3–10 coloured satellite cards, spokes, optional details and arrowheads. This is unmistakably distinct from create_cycle, create_process or create_fishbone based on the description alone.

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 an explicit selection rule ("Choose it when several items relate to one centre with no order between them") plus four concrete example scenarios. It then routes the agent away to named alternatives with their own conditions: cycle for repeating sequences, process for one-way steps, mind map for branching, org chart for reporting lines.

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