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

The description discloses that the tool appends and auto-wires an edge, describes what happens with after='none' (parallel branch head), and importantly states it 'Returns the rig's fresh block-by-block summary — read it back to the user; the Builder canvas updates live.' This adds real behavioral context beyond the annotations, which only indicate non-read-only, non-idempotent, non-destructive. No contradiction with annotations.

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?

The description is front-loaded with the core action, then covers wiring behavior, return value, and alternative tool in a compact sequence. Every sentence earns its place; there is no filler or repetition of schema data.

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?

Despite having no output schema, the description names the return value ('fresh block-by-block summary') and tells the agent to read it back to the user. For a tool with a complex nested node object, it gives enough operational guidance to invoke it correctly, including the live canvas update behavior.

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 100%, so the schema already documents all parameters. The description adds value by clarifying the semantics of `after` (default, id/label/position, 'none') and by noting that node fields match rig_author's nodes, which helps the agent reuse existing knowledge of node structures.

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 verb and resource: 'Add ONE block (graph node) to a canvas rig'. It distinguishes itself from the sibling rig_author by calling itself 'the granular edit' and 'the scalpel', which immediately clarifies its narrow scope relative to whole-rig authoring.

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 explicitly says 'For whole-rig authoring use rig_author; this is the scalpel', naming the alternative and the condition for choosing it. It also explains the three wiring modes (default after last block, after a specific node, or unwired with after='none') which tells the agent exactly how to direct the operation.

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