update_cel

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

Annotations already declare readOnlyHint=false and destructiveHint=false, so the safety profile (a non-destructive mutation) is established structurally. The description adds no behavioral context beyond that: nothing about batch-vs-live backend semantics, the save flag, permission requirements, or reversibility, despite 'save' and 'backend' being significant controls.

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 led by the verb, with the field list acting as an efficient index of capabilities. No filler or redundancy, though the run-on list format prioritizes brevity over scanability.

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 15-parameter mutation tool with no output schema and under-half schema coverage, the description covers the primary content fields but leaves the operational controls (save, backend, sprite, layer) unexplained. Adequate as a capability summary, incomplete as invocation guidance.

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?

With schema coverage at only 47% and 15 parameters, the description compensates well by clarifying the meaning of bare parameters the schema leaves undocumented — that x/y are absolute and dx/dy relative, and that it can set color, data, and properties. It omits save/backend/layer/sprite meaning, but it materially strengthens several otherwise opaque fields.

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 ('changes') plus the resource ('cel') and enumerates the mutable surface: position, opacity, z-index, color, data, properties, and frame relocation. An agent can tell this is the cel-mutation tool, though it never explicitly distinguishes itself from siblings like copy_cel, delete_cel, or link_cels.

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, when-not-to-use, or alternatives guidance is provided. The field enumeration implies context, but the agent gets no help deciding between update_cel, copy_cel, draw_pixels, or link_cels for a given mutation task.

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