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

Goes well beyond the readOnly/idempotent/non-destructive annotations: it discloses the check vocabulary (passed, needs_review, disagrees, failed_sanity_check), instructs that non-passing facts be treated as unverified and cited by page, and states 'never extracts, never bills' so cost/side-effect expectations are explicit. It also notes the max_facts truncation signal in context.

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 core purpose and free of filler, with the scoping/workflow guidance up front where it matters. The middle sentence carrying the check-status list and section taxonomy is long and slightly tangled at 'and checks', but no sentence is disposable.

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 read-only, six-parameter tool with a full output schema, everything an agent needs is present: auth, discovery path, narrowing strategy, how unverified facts must be handled, and the build sibling for the unsupported case. Nothing forces a guess before calling.

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 baseline is 3; the description still adds workflow meaning the schema cannot express — that omitting options yields just the summary, and that a single `pin` or `search` is the way to bound result size. It repeats less than it adds, but the per-parameter semantics themselves are largely left to the schema.

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 — reading the UCM digital twin of one already-extracted datasheet — and enumerates the fact taxonomy (pins, whole_part, interfaces_rails, registers, checks). It explicitly carves itself apart from the extract_* siblings by noting it reads stored results only, and names the build sibling for unextracted parts.

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 concrete call sequence: first with no options for the summary, then narrow via `sections`, `pin` or `search` to keep the answer small. It also routes discovery to datasheetvend_list_component_twins and the not-yet-extracted case to datasheetvend_build_component_twin, and states the API key prerequisite.

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