pcb_apply_via_template

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

With no annotations, the description carries the full burden and does: it warns that growing vias can create clearance violations and instructs running DRC, notes the template link cannot be read back so must be verified in the Properties panel, and documents refusal codes LOCAL_STACK and NO_ANNULAR_RING. That is unusually rich disclosure 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 action, then mechanics, caveats, and Args/Returns. Most sentences earn their place, though the FormatCopy provenance sentence and the verbose Returns paragraph add some bulk that could be trimmed.

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 six-parameter mutation tool with no annotations, the description covers trigger, preconditions, filtering, safety warnings, error codes, and a return summary. Even though an output schema exists, the extra failure-mode detail is genuinely additive rather than redundant.

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 0%, so the description must compensate, and it does: all six parameters are explained with units (source_x/source_y in mils, from_size_mils/from_hole_mils as 'only vias at this size now'), and dry_run's contract ('report what would change and change nothing') is spelled out. The filter semantics of net are also stated.

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 concrete verb and resource with scope: 'Make free vias match a source via: its via template, hole and diameter.' It is clearly distinguishable from neighboring tools like pcb_normalize_vias, pcb_place_via, or pcb_set_via_soldermask_relief because it names the exact properties propagated (template link, mode, hole, diameter) and the 'free via' target set.

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 a clear precondition ('Point at a via that already uses the template you want') and a motivating scenario ('bring a board in line with a Routing Via rule in template mode'). It stops short of explicitly naming alternatives to use instead when no template-mode rule exists or when vias are not free, so it's clear context without full exclusion guidance.

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