Get search volume and metrics

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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds genuine behavioral detail beyond that: results are historical, and close variants grouped by Google are returned alongside the queried keywords, which affects how the agent should interpret output volume.

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?

Three tight sentences: purpose plus returned metrics first, then usage guidance, then an output caveat. No filler and no repetition of schema details the agent will read anyway.

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 no output schema, the description usefully enumerates what comes back (average monthly searches, competition, top-of-page bids, trends) and warns about grouped close variants, which is the key interpretive detail. Minor gaps remain around what happens for keywords with no data and any quota/cost implications of a 10,000-keyword lookup.

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 86%, so nearly every parameter is already documented in the schema (network, keywords limits, language formats, month patterns, locations). The description only implicitly touches parameters via 'historical' (date range) and 'close variants' (keyword handling), adding little beyond the schema — 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 specific verb and resource ('Get historical Keyword Planner metrics for specific keywords') and enumerates the exact metrics returned (monthly searches, competition, bid range, trends). This is clearly distinguishable from the discovery-oriented sibling generate_keyword_ideas.

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 sentence 'Use this to check exact keywords rather than discover new ones' gives an explicit when-to-use and a when-not, which implicitly routes the agent toward generate_keyword_ideas for discovery. It stops short of naming the sibling or covering other alternatives like forecast_keywords, so it is clear context without full exclusion coverage.

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