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

With no annotations at all, the description carries the full behavioral burden and does substantial work: it discloses the billing model (charged only when records return, exact-key misses free), the legitimate emptiness of changelog, and precise date-gated null semantics for eight fields. It still omits auth/rate-limit/pagination behavior, so it is strong but not exhaustive.

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, pricing, and caveats are front-loaded in that order, and each sentence carries distinct information about result interpretation. The three consecutive 'null before <date>' enumerations are verbose and could be compressed, keeping it out of 5 territory.

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 rightly spends its budget describing return contents (field-level null semantics, excluded contact fields, changelog exclusions), which is a real strength. But for a two-parameter tool with 0% schema coverage and a required usdot_number plus an unmentioned since_date, the parameter story is incomplete, leaving the definition only adequately complete.

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 0%, so the description must compensate, and it does not: neither usdot_number nor since_date is explained, and the several hard-coded cutoff dates (2026-09-02, -06, -12) are never tied to the since_date filter an agent is choosing. The date-heavy prose is interpretable as date-window context but adds no parameter syntax or constraints.

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 opening line names the resource and its scope precisely: historical snapshots plus changelog entries for a single carrier, which is distinguishable from the identity/lookup siblings that return current state. It lacks an explicit verb and never names a sibling for contrast, so it falls short of a 5.

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?

Usage is implied rather than stated: the pay-per-returned-record note and the 'exact-key miss is free' remark help an agent decide whether a call is worth making, and the empty-changelog caveat warns against misreading results. However, there is no explicit when-to-use-this-vs-lookup_carrier guidance, no prerequisites, and no explanation of when to pass since_date.

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