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

Annotations only declare readOnlyHint=false and destructiveHint=false; the description adds the crucial behavioral fact that target clips' existing effects are overwritten by default and preserved only when append=true. That is exactly the kind of context the annotations do not carry. It stops short of saying whether the overwrite is recoverable (undo) or how partial failures are handled.

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?

A single front-loaded sentence with no filler; the source-to-destination relationship comes first and the caveat about replacement follows immediately.

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 four-parameter mutation tool with no output schema, the description covers the essential replace-vs-append semantics but leaves the agent guessing about return value, error handling for invalid clip ids, and whether cross-project copies are permitted. Adequate, not complete.

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 only 25% — only projectId is documented — so the description must compensate. It does explain the one non-obvious flag (append=true means merge rather than replace) and clarifies fromClipId/toClipIds as one source clip onto many targets, but adds nothing about projectId, ordering, or behavior with duplicate target ids.

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 ('copy one clip's whole effect stack onto other clips'), plus the scope of the copy (the whole stack, not a single effect). It does not name a sibling such as paste_attributes or move_effect to disambiguate, but the operation itself is unmistakable.

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?

Usage is implied by the phrasing — this is the tool for propagating one clip's effects to several others — and the parenthetical tells the agent the default is a replace. There is no explicit when-not guidance and no mention of alternatives like clear_effects or paste_attributes when only part of a stack should move.

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