Read a PcbLib

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

Annotations already declare readOnlyHint=true, destructiveHint=false and closed-world, so the safety profile is covered; the description goes further by disclosing the fidelity-carrier fields, the byte-identical-rewrite guarantee, the omit-empty-rather-than-null convention, the compact default and the paging shape. It stops short of stating performance/rate considerations for very large libraries, but the operational behaviour is well disclosed.

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 use-case routing are front-loaded and every sentence carries information, so little is wasted. It is nonetheless a dense wall of prose covering several distinct topics (output shape, fidelity fields, omission rules, paging, alternatives) that would read better structured, which costs it a point.

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?

With no output schema and a 5-parameter read tool, the description carries the full burden and does so: it describes the returned JSON, the mechanical-layer naming caveat, the paging envelope fields and the omission semantics. An agent has everything needed to call it and interpret the result.

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?

With 100% schema coverage the baseline is 3, but the description adds real meaning beyond the schema: component_name 'turns paging off' (the schema never says this), compact's default and rationale, and the returned paging fields. It still doesn't fully document limit/offset edge behaviour, hence a 4 rather than 5.

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 (read) and resource (.PcbLib file) and enumerates exactly what is returned: footprints with description, height and primitives, plus mechanical_layers with kind and enabled flag. It explicitly contrasts itself with get_component, search_components and list_components, so an agent can pick it out without opening a 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?

Gives two positive use cases ('study a library's footprint style', 'fetch data for a read-modify-write') and names the three cheaper alternatives with the conditions that select them (one known footprint, name-pattern search, names alone). Nothing is left to inference.

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