Read a PcbLib

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

Annotations already set readOnlyHint=true and destructiveHint=false, but the description adds substantial behavioral detail: fidelity fields that must be passed unchanged for byte-identical rewrites, omission of empty lists/optional fields, compact-mode behavior for Simple stack_mode pads, and paging response metadata (total_count, returned_count, offset, has_more). These disclosures go well beyond the annotations and accurately predict output semantics.

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 purpose and then logically flows through usage, alternatives, data shape, fidelity rules, omission semantics, compact flag, paging, and component_name. Every sentence contributes unique functional information; there is no filler or redundancy. Its length is justified by the tool's complexity and absence of an output schema.

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 no output schema, the description covers the return format (structured JSON, units, included primitives), fidelity requirements, empty-value handling, compact-mode output, pagination metadata, and the effect of component_name. It also points to the shared JSON shape with get_component/export_library/write_pcblib, giving the agent enough context to correctly invoke and interpret results.

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?

Even with 100% schema description coverage, the description adds real meaning: 'compact (default true) omits a pad's per-layer size and shape arrays when its stack_mode is Simple', 'component_name fetches one footprint and turns paging off', and 'page with limit and offset: the result reports total_count...' These clarify how each parameter affects behavior, not just its type.

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 opens with a precise action and resource: 'Read an Altium .PcbLib file' and specifies the returned content (every footprint with description, height, primitives) and units. It also names sibling tools and their distinct use cases, allowing an agent to immediately differentiate read_pcblib from get_component, search_components, and list_components.

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 explicitly says when to use this tool ('study a library's footprint style or to fetch data for a read-modify-write') and provides clear alternatives: 'For one footprint whose name you know, get_component is cheaper; to find footprints by name pattern across libraries, search_components; for names alone, list_components.' This exceeds the minimum by giving both context and exclusion conditions.

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