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

Annotations already declare readOnlyHint=false, destructiveHint=false and idempotentHint=true, so the safety profile is covered; the description adds the important scope clarification that document content, revision and completion are untouched, which resolves the apparent tension between 'mark' and 'readOnlyHint=false'. It also discloses that read state is per-viewing-user ('for the requesting viewer') and states the request_key idempotency contract, going beyond the annotations. It doesn't mention failure behavior for unknown or unapplied change_ids, but the supplied output schema covers the response side.

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?

Four short sentences, each doing distinct work: purpose, non-effects, workspace sourcing, idempotency rule. The core action is front-loaded and no sentence is redundant.

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 small, idempotent state-marking tool with a full output schema and annotations covering safety and idempotency, the description covers intent, non-effects and the two non-obvious parameters. The remaining gap is season_id, whose scoping role is never explained, which matters given 0% schema description coverage.

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 0%, so the description carries the whole burden: it explains where workspace_id must come from, that request_key must not be reused across differing requests, and that change_ids refer to already-applied changes. However season_id (the one optional parameter) and document_id receive no meaning at all, so roughly half the parameters remain semantically bare.

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?

Specific verb+resource+scope: 'Mark these exact applied changes as read for the requesting viewer' tells the agent precisely what state is being mutated and against which entity ('these exact applied changes' rather than an open-ended document). The negative scoping ('does not change the document, its revision, or completion') separates it from apply_studio_document_edits and undo_studio_document_changes without naming them directly.

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?

It gives concrete preconditions for two parameters (workspace_id must come from the authorized Film/Series/GenAds directory; request_key may only be reused for the identical request), which is real usage guidance. It never states the trigger condition explicitly — e.g. that this should be called after reading applied changes via read_studio_document_changes to acknowledge them — and does not contrast with that sibling or with undo_studio_document_changes, leaving the when-to-use decision implied.

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