Which keyboard sizes have a key

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

Annotations already declare readOnly, idempotent and non-destructive, so the safety profile is covered. The description adds genuine domain context beyond the annotations: that results can be negative and that absent keys are typically accessed via an Fn layer, which shapes how an agent should interpret the answer.

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, front-loaded with the core question; the example list is somewhat long but functional and earns its place by clarifying valid key inputs. No wasted preamble.

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 query with no output schema, the description is nearly complete: it explains intent, input domain, and the Fn-layer nuance. It could say more about the return shape (a list of size names), but that is a minor gap against annotations that already carry the behavioral profile.

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 both parameters (key, iso) are already documented in the schema. The description's example list enriches the 'key' semantic range but largely overlaps the schema's own examples, so it adds only marginal value above the baseline.

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 ('Check which keyboard sizes have') and resource ('a key or key group'), with concrete examples of the key domain. An agent can distinguish this from list_keyboard_sizes or compare_keyboards without opening the 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?

The description gives clear context for when this tool applies (querying key/group availability across sizes) and adds a helpful caveat that missing sizes 'usually reach it through an Fn layer.' It does not, however, name a sibling or explicitly state when not to use it.

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