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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds value by saying what comes back (parts, fit checks, switch quantities, parts list), but it does not disclose what happens when no reviewed combination matches the requested size/switch/profile, which is the main failure mode for a constrained-combination planner.

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?

Two sentences, zero waste, with the core purpose front-loaded and the output summary following. Nothing is repeated from the schema or annotations.

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?

An output schema exists, so return values need not be explained, and the parameter set is small and fully documented in-schema. The remaining gap is behavioral: with zero required parameters, an agent cannot tell from the description what a no-argument call does or whether combos are chosen automatically.

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 description coverage is 100%, so all three parameters (size, switchType, keycapProfile) are already documented in the schema, establishing a baseline of 3. The description hints at the combinations concept but adds no default behavior or format guidance beyond the schema, notably nothing about all parameters being optional.

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?

Specific verb+resource: 'Plans a keyboard build' and narrows the scope to 'the website's reviewed combinations of barebones kit, switches and keycaps', which separates it from lookup siblings like find_switches or get_layout. It stops short of naming an alternative directly, so sibling differentiation is inferential rather than stated.

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?

'Plans a keyboard build' plus 'reviewed combinations' implies the use case — get a validated parts combination rather than raw part data — but there is no explicit when-to-use or when-not-to-use statement, and no pointer to which sibling to use instead for individual part lookups.

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