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

Annotations declare it is a non-read-only, non-destructive, closed-world operation, matching "refill". The description adds the useful scope detail that ALL zones are refilled (no subset targeting), but says nothing about it being a potentially long-running job that may return status "running" and must be polled — that behavior lives only in the wait_s schema text.

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, front-loaded sentence with zero filler; the verb and scope appear immediately.

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 mutating, possibly async job with no output schema, the description covers only what. Workflow placement and the need to follow up with get_board_job on a "running" result are left to the parameter schema, which is thin compensation.

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 100%, so design_id and wait_s (including the running/polling semantics and the 55s cap) are fully documented in the schema. The description adds nothing on either parameter, which is acceptable at this coverage level but not value-adding.

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 ("Refill") and resource ("every copper zone"), plus the underlying engine (KiCad's zone filler), so the agent knows exactly what happens. It doesn't name the sibling boundary (e.g. set_zones defines zones, this recomputes fill), but the operation itself is unambiguous.

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?

No guidance on when to run it — not after routing, not after moving footprints, not after set_zones/set_keepouts changes — and no mention of alternatives or prerequisites. The agent must infer the workflow position from the sibling list alone.

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