user_tool_state

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

No annotations are supplied, so the description carries the full behavioral burden. It does disclose that the tool returns the current state and inverts read/write based on argument presence, but it says nothing about whether setting overwrites the user's existing brush mid-session, whether changes persist, whether partial updates leave unmentioned fields untouched, or what validation errors look like.

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 sentences, front-loaded with the read/write distinction, with no filler. The mid-sentence line break and the 'e.g.' aside are slightly awkward but the content is tight for the space used.

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?

With 8 undocumented parameters, no annotations and no output schema, this definition is too thin for the tool's complexity. An agent can tell roughly what the tool is for but not how to construct a valid call — the units for size/opacity, valid blend_mode and preset values, and the interaction between eraser and the colour fields are all unknown.

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 0% across 8 parameters, so the description must compensate and largely fails to. It hints only at two categories ('colours' and 'brush'), leaving flow, size, eraser, preset, opacity, background, blend_mode and foreground completely unexplained — no units, ranges, accepted preset names, or colour formats.

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 a specific verb+resource pair: read or set the colours and brush the USER paints with. The explicit emphasis on 'the USER paints with' distinguishes it from agent-side brush tools like brush_stroke or list_brush_presets, though the purpose of the dual read/write mode is only implied by the parenthetical '(no arguments)'.

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?

'Read (no arguments)' gives a concrete condition for the read path, and 'hand them the palette colour or brush you used' gives one motivating use case for the set path. However, there is no guidance on when to prefer this over siblings such as brush_stroke, list_brush_presets or palette_colors, and no statement of when setting state would be inappropriate.

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