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

Annotations only declare idempotentHint=true, so the description carries the behavioral burden and does so well: it discloses the auth requirement (logged-in/organizer), that preview writes nothing, that PUBLIC visibility is irreversible for what others have already seen, that deletion requires separate confirmation and is unrecoverable, and that per-item failures land in `failed` rather than aborting the batch. Nothing here contradicts the idempotency hint.

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 precondition, then workflow, then risk, then sibling routing — a logical order with dense semicolon-separated clauses. It is packed and slightly run-on, but every clause (limits, preview, irreversibility, alternatives, failed handling) carries information an agent needs.

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 batch-mutation tool with no output schema, the definition covers auth, id sourcing, item limit, preview/execute split, irreversibility warning, alternative tools, and partial-failure reporting. An agent has everything needed to call it safely and correctly.

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 schema baseline already documents `items`, `activityRef` and `preview`. The description adds meaning beyond it by explaining how `materialId` values are obtained, how preview relates to execution, and the 50-item cross-event limit that governs the array parameter.

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 (rename/change visibility), resource (activity materials, `materialId`), and scope (batch, up to 50, cross-event) up front. It explicitly names the upload and delete siblings it is not, so an agent can separate it from add_activity_material/remove_activity_material without reading any 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 an explicit acquisition path (get ids via list_activity_materials), a mandatory two-step workflow (preview=true first, then omit preview to actually execute), and routes alternative intents to add_activity_material, prepare_activity_material_upload, and remove_activity_material. When-to-use and when-not-to-use are both covered.

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