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

Annotations already declare this is a non-read-only, non-idempotent, non-destructive mutation, so the safety profile is partly covered. The description adds real value by stating what is preserved (shading, detail, other hues, background) and the six-second tracked-window limit. It does not say what happens on repeated invocation (despite idempotentHint=false) or what the response contains.

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: the core action and its preservation guarantees come first, the hard operational constraint second. No filler, no restatement of the title.

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?

Given a 9-parameter mutation with no output schema and near-zero schema descriptions, the definition covers intent and one hard constraint but leaves prerequisites, range semantics, and the tuning parameters unexplained. An agent could call it, but would likely guess at tolerance/intensity and at whether start/end are required in practice.

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 11% (only project_id documented), so the description must compensate and largely does not. It maps object_id, from_colour and colour implicitly and gestures at start/end via the six-second window, but intensity, tolerance, and id are never explained even though tolerance and intensity directly control how aggressive the color match is.

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 ('changes a selected tracked object's specified source color to a requested color'), which is clearly distinct from siblings like set_color_grade or isolate_colour. It stops short of naming an alternative, so an agent must infer the contrast rather than being told it.

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?

'Selected tracked object' implies a prerequisite (select_object / track_point must have run), which is useful implied guidance. However, there is no explicit when-to-use vs when-not, and no reference to adjacent tools such as isolate_colour, match_grade, or set_grade_custom that an agent could easily confuse with this.

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