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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint, so the safety profile is covered. The description adds non-obvious behavioral detail beyond that: the response changes shape depending on whether the input resolves to a brand (returns brands with device counts) or a recognized brand (returns its homologated models), which an agent could not infer from annotations alone.

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 resource and the mode-switching behavior, followed by the routing advice. Every clause carries information; nothing is redundant.

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 an output schema present and 100% parameter coverage, the description only needs to convey the tool's role and the dual response mode, which it does. The one small gap is not stating that matching is prefix/substring-based or how ambiguity with many brand matches should be handled, but this is minor for a typeahead.

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 the 'query' partial-name semantics and the 'locale' enum are fully documented in the schema. The description reinforces the partial-name resolution concept but adds no format or syntax detail beyond what the schema already provides, making baseline 3 correct.

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 ('Typeahead for the Synergrid C10/26 list') and spells out both return modes — matching brands with device counts, or a recognized brand's homologated models. That is enough to distinguish it from check_inverter_c10_26 without opening either 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?

It gives an explicit precondition and ordering: 'Use this to resolve an ambiguous device name before calling check_inverter_c10_26,' naming the sibling it feeds into. It stops short of saying when not to use it (e.g., when the exact brand/model is already known), so it is clear context rather than full when/when-not guidance.

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