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

Annotations already declare destructiveHint=true, idempotentHint=true and readOnlyHint=false, so the safety profile is covered. The description adds genuinely useful non-obvious behavior: 'Moving a source does not move existing clips or change branding,' which is not derivable from annotations or schema. It stops short of 5 because it does not clarify the detach path (e.g. that seriesId null means detach) or any permission requirements.

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?

Two tight sentences with no filler, and the core verb list is front-loaded. It is appropriately sized for the tool, though the second sentence's caveat could be tied more explicitly to the move operation.

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?

An output schema exists so return values need not be described, and annotations carry the destructive/idempotent profile. However, for a 6-required-parameter mutation, the description leaves idempotencyKey, workspaceId and the assign-vs-move-vs-detach semantics underexplained, and gives no routing against sibling series tools.

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% for 6 parameters. The description only illuminates expectedSeriesId (and implicitly seriesId via 'detach') and the kind enum ('source or project'). contentId, workspaceId and especially idempotencyKey remain completely unexplained, so the description does not compensate for the coverage gap.

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 specific verbs and resources: 'Assign, move or detach one source or project.' An agent can tell it manipulates series membership for a single content item. It does not, however, differentiate itself from the sibling 'series_apply' or explain the assign/move/detach distinction, so it stops short of a 5.

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?

No when-to-use guidance is given. The description never says when this tool is preferred over the sibling 'series_apply', nor when a caller would detach versus move. The mechanism 'using expectedSeriesId' is mentioned but no preconditions or exclusions are stated.

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