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

With no annotations, the description carries the full burden and does well: it discloses the output scale (0-100 + volume), and that rate limiting/quota exhaustion can occur along with the correct user-facing message. It stops short of describing auth requirements, latency, or truncation of long historical ranges.

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?

Four tight sentences, each doing distinct work (what it returns, positive use case, two negative routings, error handling). No filler and the return format is front-loaded.

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?

No output schema exists, and the description compensates by stating the value range and the optional volume field. Combined with explicit sibling routing and quota guidance, an agent has enough to call it correctly; only deeper return-shape detail (e.g. date granularity) is absent.

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% and the schema already spells out valid sources and per-source keyword formats, so the description adds little beyond 'one keyword and one source'. Baseline 3 applies when the schema does the heavy lifting.

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 ('Full historical series for one keyword and one source') and quantifies the return ('0-100 values, plus volume when available'). It also explicitly distinguishes itself from both siblings, so an agent can route without opening any 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?

Gives explicit when-to-use ('charting or custom math'), when-not ('Not for live "what's trending now" boards'), and names the alternative for each case (get_top_trends, get_growth). It even covers the error path by telling the agent what to say when rate limited or out of quota.

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