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

Goes well beyond the annotations: it discloses which playback keys are non-settable on converted image slots, that the engine forces loop/muted/no-controls and picks autoplay per surface, that converted slots inherit the image slot's fit/ratio, that template video_url slots accept no playback, that `remove` reverts converted slots to pictures, and that unset video slots are filled from stock footage. This is exactly the extra context annotations can't carry.

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?

Front-loaded with the core action, then layers slot types and edge-case behavior in ordered sentences. Dense but largely earns its length; the nested parentheticals and one long compound sentence push it just short of a 5.

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 3-parameter mutation tool with no output schema and 67% schema coverage, the description supplies the missing semantics (slot tokens source, conversion behavior, non-settable keys, remove semantics, empty-slot fallback). An agent has what it needs to call this correctly without further lookups.

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?

Adds real meaning to the nested `playback` object, defining startTime, preload, mobile ('poster' = still only on phones) and overlay (0-100% black), and explains `remove` maps to converting image slots back. Slight tension remains: the schema lists loop/muted/autoplay/controls/fit/ratio while the description says they are not settable here, which could confuse the exact payload, so not a 5.

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+resource ('Put a clip in a slot') and immediately distinguishes the two slot flavors it covers (VIDEO `video_url_…` vs IMAGE `image_url_…`/`portrait_image_url_…` converted to video). An agent can tell this apart from sibling setters like uichemy_set_images and uichemy_set_image_display without opening 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 routes the agent to uichemy_get_page and uichemy_template_slots for slot tokens, and names uichemy_set_image_display as the owner of fit/ratio for converted slots. It explains context clearly but does not frame when NOT to use this tool versus a dedicated image or playback setter beyond that one cross-reference.

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