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

Annotations already declare readOnly/non-destructive/closed-world, but the description goes well beyond them: it discloses the datasheet-database enrichment merged into topology_constraints, the footprint_suggestions, and critically that the 'custom' path returns an UNVERIFIED machine-extracted pinout that is 'not a symbol.' It also explains the design_id side effect (lookup recorded for the dossier; registered part belongs to the design). This is exactly the behavioral context annotations cannot carry.

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 return contents before the usage guidance and the custom-library edge case, and most sentences earn their place. There is mild redundancy (topology_constraints is introduced twice) and the run of clauses makes it denser than necessary, but it is well-structured overall.

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?

No output schema exists, yet the description covers the return contents (pins, description, topology_constraints, footprint_suggestions), the merge behavior, the custom fallback and its caveat, the batch form, and the design_id side effect. For a 4-param read tool with full schema coverage, nothing an agent needs to call it correctly is missing.

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, but the description adds real semantics the schema does not: the special library='custom' + name='<part number>' convention, the batch form of up to 12 (library, name) pairs, and the meaning of passing design_id. It stops short of describing error behavior for a not-found symbol, so not a 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?

The description names a specific verb and resource ('Return the full pin list (number, name, electrical type) and description for a specific KiCad symbol') and clearly distinguishes itself from the sibling search_kicad_symbol by being a direct lookup and by handling the non-KiCad 'custom' fallback. An agent can tell it apart from create_custom_symbol and search_kicad_symbol without opening any 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?

Explicit when-to-use: 'Use this before writing pin connections ... so names, constraints and footprints match the symbol exactly.' It also names the routing condition to the alternative: for a part NOT in KiCad, call this with library='custom', then register with create_custom_symbol. When/when-not and the alternative tool are all stated.

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