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

Adds substantial context beyond the readOnly/idempotent annotations: it is FREE, purely local, with no upstream call, no billing, and no market dependency. It also discloses a real limitation — navigational detection only covers destination/account phrasing, and brand-name navigational queries deliberately return `unknown` rather than a guessed label.

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 purpose and output labels, then the operational characteristics, then the caveat. It is dense but long, and a few clauses (the 'free-tier fallback' lineage) serve explanation more than invocation, keeping it just under 5.

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 two-parameter, no-output-schema tool this is close to complete: it names the labels, the input bounds, the cost profile, and the accuracy limitation. The one gap is the return shape (e.g., per-keyword label mapping vs. a plain list), which neither the description nor an output schema specifies.

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 both parameters are already documented; the description only echoes the 1-200 keyword bound that the schema's minItems/maxItems already encode. It adds no format guidance for keywords or projectId beyond the schema, so the baseline 3 applies.

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 precise verb+resource (classify keywords' search intent) and enumerates the exact output labels, so the agent knows what it produces. It also distinguishes itself from keyword research by noting it operates on wording alone 'with no research/volume data yet'.

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 clearly frames when this is the right call: a bare keyword list that has no research/volume data yet, using the same heuristic research_keywords applies as its free-tier fallback. It stops short of explicitly naming a sibling alternative and stating when NOT to use this (e.g., when volume/CPC data is required).

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