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

Annotations already establish the safe read-only profile (readOnlyHint=true, destructiveHint=false, openWorldHint=false), so the bar is lower. The description adds real context beyond them: what gets drawn, that the pixel-per-mm scale and region are returned for exact follow-up crops, and the concrete output location (workspace.render.png).

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 dense paragraph with the core purpose front-loaded and the option semantics following. Every clause carries information (feature list, options, output behavior, download path) and none is wasted.

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 no output schema, the description carries the return burden and does so: it says the scale and region come back and where the PNG is downloaded. For a 14-parameter render tool the description, together with the schema-level notes on wait_s, region and design_id, covers enough for correct invocation.

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 coverage is only 21%, so the description must compensate, and it largely does: it gives the enum for side, explains region as a mm crop, and clarifies what drc_markers, ratsnest, highlight_nets/highlight_refs (magenta) actually draw, plus refs, layers and courtyards in prose. Only markers, max_width and px_per_mm go unexplained, so it earns above the low-coverage baseline.

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 (render) and resource (board) with a clear qualifier (2D, exact). The feature list (copper per layer, pads, vias, pours, outline, courtyards, refs) lets an agent distinguish this visual-render sibling from analysis tools like board_census, get_board_info or check_physics 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?

Usage is implied ('as an engineer reads it', follow-up crops, visual inspection) but the description never states when to reach for this versus alternatives such as get_board_context, run_drc, or board_census. No exclusions or prerequisites are named, leaving routing to inference.

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