pcb_modify_layer

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

With zero annotations, the description carries the burden and does disclose a genuinely non-obvious behavior: optional parameters are applied only when provided (non-empty string / non-zero number), which warns the agent it cannot reset a value to zero/empty. It also discloses the underlying API targets and that a confirming dictionary is returned. Missing are failure modes (nonexistent layer) and confirmation/reversibility, keeping it short of a 5.

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?

Purpose is front-loaded and the field-mapping table plus Args list is readable. There is mild redundancy, since name, copper_thickness_mils and the dielectric fields are explained twice (mapping block and Args block), costing some space without adding information.

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 7-parameter mutation tool with 0% schema coverage and no annotations, the description supplies parameter meaning, units, enum values, and partial-update semantics. An output schema exists so return values needn't be documented. Remaining gap is error/precondition behavior for a nonexistent layer, which matters for a mutation tool.

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%, so the description must compensate fully, and it does: every one of the 7 parameters is explained with units (mils), semantics (Dk value, dielectric material string), and even an enumerated value set for dielectric_type that the schema does not encode as an enum. This is exactly the value-add the schema lacks.

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 and resource: modify/tune properties on an existing copper layer. This clearly separates it from siblings like pcb_add_layer and pcb_remove_layer, though it never names those alternatives explicitly. An agent knows what the tool does 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 rather than stated: it operates on an *existing* layer and applies only supplied fields, so the agent can infer it is an edit-not-create tool. However, there is no explicit when-to-use/when-not guidance and no routing to alternatives such as pcb_get_layer_stackup for reading values or pcb_add_layer for creating a layer.

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