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

Goes well beyond the readOnly/idempotent annotations: discloses ~30 s latency per live call, the $0.03 charge per successful call, that bad input is free but upstream errors and empty results (insufficient Google data) are still billed, and that payment is passed via _meta["x402/payment"] over USDC on Base. These are exactly the operational facts an agent needs before calling a paid, slow endpoint.

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-loads purpose and return shape, then cost/latency/payment in descending priority; no sentence is idle. It is a single dense block, though, and the pricing/payment sentences could be split for scannability.

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?

There is no output schema, so the description supplies the return shape itself (top related queries 0-100, rising queries as % growth), and it covers the commercial and failure-mode context (cost, latency, empty-result billing). Nothing an agent needs in order to call this correctly is missing.

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% — country codes, keyword constraints, and the timeframe enum are all documented inline. The description only echoes the scope in prose ('for a country or worldwide, past 7 days to 5 years') without adding format or edge-case detail beyond the schema, so 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+resource (related queries for one keyword) and enumerates the two returned series — top related searches scored 0-100 and rising queries as % growth — plus the scope axes (country/worldwide, 7 days to 5 years). An agent can tell this apart from a generic trends lookup without reading 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?

Explicitly names the use case: query expansion, content ideas, emerging searches around a keyword. However, it never names the adjacent siblings (keyword_ideas, google_trends_by_region) or states when this is the wrong choice, so routing between overlapping tools is left to inference.

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