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

Annotations only declare read-only/non-destructive/closed-world, and the description goes far beyond: it defines the four snapshot windows, warns they are raw baselines not calculated changes, discloses that pagination exists only for BROWSE and lacks total/hasMore, and caps FUZZY at 100 Lucene matches. Field-level semantics (percentage ranges, supplyDemandRatio formula, MATCHED vs NO_MATCH) remove ambiguity an agent could otherwise get wrong.

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?

Purpose and marketplace scope are front-loaded, followed by mode behavior, then output-field semantics, then a disambiguation line. It is dense and mostly earns its length, but the eight marketplace names/IDs duplicate the enum descriptions verbatim, which is redundant.

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?

An output schema exists, so return-value explanation was optional, yet the description documents the snapshots, trend points, percentage semantics and status values — precisely the parts of a complex analytics payload an agent needs to interpret. Nothing material for correct invocation is missing at 8 parameters.

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%, so the baseline is 3, but the description adds cross-parameter rules the schema only implies per-field: pagination and sorting apply only to BROWSE, EXACT requires 1-100 complete terms, FUZZY takes exactly one keyword. Some of this repeats the schema's per-property text rather than extending it.

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: 'Query the latest Amazon Brand Analytics search-term report for one supported marketplace'. It also explicitly bounds itself against siblings at the end: 'not keyword-rank tracking or advertising search-term performance', which separates it from query_keyword_rank_* and query_advertising_search_terms.

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 states the modes and their constraints (BROWSE paginated, EXACT 1-100 terms, FUZZY one keyword, neither accepts pagination or sorting) and gives negative guidance against related tool categories. It does not explicitly name the closest sibling, query_aba_search_term_trends, as the alternative when trend history rather than a single report snapshot is wanted.

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