pcb_create_diff_pair

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

With no annotations, the description carries the burden and does disclose that this is a mutating creation step, its prerequisite, and its downstream effect (enabling differential routing / impedance constraints). It does not say what happens on failure (e.g. missing net, name collision) or whether re-creating an existing pair errors, which keeps it out of the top band.

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 and precondition are front-loaded, and the args block is compact and scannable. The Returns section duplicates what the output schema already conveys, so it is slightly redundant, but nothing else is wasted.

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 3-parameter mutating PCB tool with no annotations, the description covers purpose, prerequisite state, parameter meaning, and expected result — enough for correct invocation. Missing error/edge-case behavior (duplicate pair, unknown net) is the only notable gap, and the existence of an output schema reduces the need to explain returns.

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% (titles only), so the description must compensate and does: it explains each argument, gives concrete example values ("USB_DP"/"USB_DM"), and documents the default naming convention for the optional name. That is materially more information than the schema provides.

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 first sentence states a specific verb and resource: create a differential pair object from two existing nets. It is clearly distinct from siblings such as pcb_get_differential_pairs (read) or pcb_create_net_class (different resource), though it does not name those siblings explicitly.

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?

The description gives a concrete precondition — both nets must already exist on the board, typically after update_pcb/ECO — which tells the agent when this tool is applicable and what must happen first. It does not spell out an explicit 'do not use when' clause or name an alternative tool, so it stops short of a 5.

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