Set Poster Frame

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

Annotations declare readOnlyHint=false/destructiveHint=false, and the description adds the critical behavioral fact those annotations cannot convey: the call is a guaranteed failure that leaves the item unchanged. Disclosing the no-op/failure semantics is exactly the context annotations omit.

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?

One compact sentence leads with unavailability, then states behavior and the workaround. No filler, every clause carries load.

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 stub with an output schema already present, the description supplies everything an agent needs: it cannot succeed, it changes nothing, and where to do the task manually. Nothing relevant 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% for both item_id and time_seconds, so parameters are already fully documented. The description adds no parameter detail, but none is needed given the tool never succeeds; baseline 3 applies.

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?

The description states the exact operation, the platform limitation that blocks it ('Premiere's scripting API cannot set a project item's poster frame'), and the observable outcome ('Fails without changing the item'). An agent knows immediately this is a non-functional stub and cannot confuse it with working siblings like set_clip_properties or set_project_panel_metadata.

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 explicitly tells the agent when not to use this tool and names the concrete alternative: do it in the Project panel with the Shift+P shortcut. There is no ambiguity about routing.

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