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

Even with readOnlyHint=true in annotations, the description adds substantial behavioral context: the FULL store scope, filter composition semantics, volume provenance (amazon_sqp vs estimated_from_rank with volume_band), rank_change comparison window (~4 periods), and the estimator calibration block. These details meaningfully go beyond the structured annotations.

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?

The description is dense but every sentence earns its place. It front-loads the core purpose, then systematically covers filters, per-term output fields, calibration data, and sibling tool routing. No filler or restatement of the title exists.

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?

Despite lacking an output schema, the description fully specifies what each returned term includes (rank, volume quality, rank_change, top-3 ASINs with click/conversion shares) and the estimator block. Combined with parameter details and sibling guidance, an agent has everything needed to invoke this tool correctly.

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?

With only 33% schema coverage, the description compensates by naming and explaining nearly all functional parameters: contains (substrings, ANDed), department, rank_max, min_volume, period (WEEK/MONTH, with MONTH = monthly volumes), and sort options. It adds semantic value beyond the schema, and the few not mentioned (limit, offset, seller_connection_id) are already self-explanatory or documented in the schema.

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 opens with a specific verb and resource: 'search the FULL Top Search Terms store by phrase - not anchored to any ASIN.' It immediately distinguishes this tool from keyword_finder by inversion (term-first vs ASIN-anchored), making its purpose unmistakable and well-differentiated from siblings.

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?

Explicit guidance is given: 'Use keyword_finder for ASIN-anchored lookups; this tool for term-first research. For the guided process start with keyword_opportunities.' This tells the agent both when to use this tool and which alternatives to use in other scenarios, leaving no ambiguity.

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