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

Annotations only declare the generic safe-mutation profile; the description goes further by disclosing that no validation happens here ("Nothing is checked here"), that nets must already exist on the board, and how to undo via ripup_routing. It does not cover failure behavior for a missing net, but the net-existence precondition is a real, non-obvious constraint the annotations do not carry.

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?

Four short sentences, front-loaded with what gets created, then defaults, then preconditions, then caveats/follow-ups. No filler and no restatement of the name or 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?

For a mutation tool with no output schema, the description covers purpose, defaults, preconditions, verification and reversal — enough to call it correctly. Minor gaps (batch limits of 500 vias / 200 tracks, error behavior on an unknown net) are covered by schema constraints or left implicit.

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 50% schema coverage, the description compensates where it matters most: width_mm, diameter_mm and drill_mm "default to the board's current track and via sizes," which is not inferable from the schema. wait_s and design_id are well documented in the schema itself, and the track/via shapes are described structurally.

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?

"Lay exact copper by hand ... tracks as polylines on one copper layer, and through vias" names a specific verb (lay copper) plus both resources (tracks, vias) and their shape. The phrase "where the routers leave a gap" cleanly separates it from route_board (automatic) and ripup_routing (removal), so an agent can pick it without opening a 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?

It gives an explicit usage context (manual touch-up after the router) and names the follow-up and undo paths: run_drc afterwards, ripup_routing to remove copper. It stops short of an explicit exclusion such as "do not use for bulk routing — call route_board instead," so it is clear context rather than a full when/when-not rubric.

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