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

Annotations already cover the safety profile (readOnlyHint=false, openWorldHint=true, idempotentHint=false, destructiveHint=false). The description adds substantial behavioral context beyond them: login/organizer requirement, server-side fetch into private storage, image moderation, broadcast of 'material online' to registrants for SLIDES/FILE, visibility defaults, 30MB size cap, direct-link requirement, and a pre-call confirmation step. This is rich disclosure.

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?

Well-structured with bracketed sections and the login/organizer requirement front-loaded. It is dense but each section (purpose, chain, pitfalls) earns its place. Slightly long, but the length is justified by the number of important constraints it must convey.

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?

Complete for a mutation tool with no output schema. It covers authentication requirements, server-side behavior, workflow ordering, visibility defaults, size limits, link requirements, and a pre-call confirmation instruction. Nothing critical for correct invocation is missing.

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 the baseline is 3. The description adds meaningful semantics beyond the schema: default visibility logic (PHOTO defaults to PUBLIC, other kinds to REGISTERED), kind-specific broadcast behavior, the 30MB per-file limit, and the direct-download-link constraint. It does not add much for activityRef, but overall it exceeds the schema baseline.

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: registering a public web file link as an activity material. It names supported material types (handout PDF/PPT, document, photo) and explicitly differentiates from siblings through the chain pointing to list_activity_materials and update_activity_material. An agent can identify what this tool does without inspecting the 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?

Explicitly gives the workflow chain (this tool → list_activity_materials to verify → update_activity_material for renaming/visibility) and a concrete alternative for oversized files (>30MB use web /pro direct upload). These are named alternatives with the conditions that select them, leaving little to inference.

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