fanout_pad

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

Annotations already declare a non-read-only, non-destructive, non-idempotent mutation. The description adds genuine behavioral context beyond them: the automatic geometric constraints it must satisfy and the hard 'never via-in-pad' rule, which tells the agent what the tool will and won't do. It omits failure behavior (e.g. what happens if no valid spot exists) and any undo/permission guidance.

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 core action and then the use cases, with no filler. The parenthetical constraint list is dense but every item is meaningful, so it stays readable without wasted words.

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 annotations present and no output schema, the description covers what it does and when to use it, but with 0% schema coverage on five parameters it leaves key invocation details (layer, distance, width, what ref/pad strings look like) undocumented, and does not say how it behaves when no valid via spot is found.

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 five parameters, so the description carries the full burden of explaining them. It mentions only the pad implicitly; ref, layer, max_dist_mm, trace_width_mm, and the search bound implied by 'nearest' are never explained, so the agent cannot reason about default 3mm distance or trace width from the text.

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 operation on a specific resource: place a fanout via plus a short trace from a single pad to the nearest valid via spot. The clearance constraints ('clear of other nets, every pad, holes, keepouts and the edge; never via-in-pad') make it clearly distinct from manual siblings like add_via or stitch_vias, though those siblings are never named.

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 explicit when-to-use cases ('connect a GND pad that routing cut off from its pour, or power-pin fanout before autorouting'), which gives an agent real context for choosing this over add_via. It stops short of stating when NOT to use it or naming the sibling alternatives, so it falls below the 5 tier.

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