Draw with ASCII grid

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

With no annotations supplied, the description carries the full burden and does disclose a meaningful side effect implicitly through the schema-backed 'clear' behavior, plus target semantics (layer, frame, project offsets, mirroring, scale). It still omits what happens to existing pixels when clear is false, what the call returns, and whether a missing layer/frame is created or an error - notable gaps for a mutation tool.

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 instruction and backed by a compact inline example that removes ambiguity about grid/legend shape. Slightly dense with stacked clauses and a stray punctuation artifact ('"." / space = transparent'), but nearly every sentence adds usable information.

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 12-parameter tool with no output schema and no annotations, the definition covers the essential call pattern, the legend fallback, multi-frame authoring, and targeting scope. Remaining gaps (return value, layer auto-creation, mirrorY behavior) are modest relative to how much of the invocation contract is already conveyed.

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 already 83%, so most parameters are documented structurally. The description does add real value for the two most confusing inputs - the legend value grammar (hex, semantic role, palette index, 'ramp:3', 'transparent') and the grid multi-frame '---' convention - but says nothing about at, scale, mirrorX/mirrorY, durationMs, or namePrefix beyond the schema.

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 ('write the sprite as text rows') and spells out the exact representation (one character per pixel, mapped through legend). It also positions itself against the sibling set as 'THE PRIMARY DRAWING TOOL for LLMs', so an agent knows to prefer it over the lower-level drawing siblings.

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?

Gives clear operational guidance: default to text-row drawing, use '---' lines to produce multiple animation frames in one call, and omit legend to fall back to auto-mapped palette roles. What it lacks is an explicit statement of when NOT to use it (e.g. versus sprite_draw_ops for precise op sequences or sprite_generate for produced art), so the agent must infer the boundary.

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