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

With no annotations supplied, the description carries the full behavioral burden and does substantial work: it discloses atomicity, the immutability of capacity and refillPerSecond after first use, the refusal behavior on mismatched settings, the retryAfterMs refusal contract, and idempotency via requestId with a 24 h stored response. The final sentence is cut off mid-word, so the idempotency guidance is incomplete, and authentication/tenancy behavior from the schema is not restated.

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?

Information is front-loaded and dense with no filler sentences, which suits a low-level primitive. The definition is visibly truncated mid-word ('charged twi'), which is a structural defect that leaves the reader hanging and signals an incomplete definition rather than a stylistic choice.

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?

Given seven parameters, four required, no annotations, and no output schema, the description does well to state the return contract (allowed, remaining, retryAfterMs) inline. It is still incomplete: the truncation removes the rest of the idempotency rationale, the peek operation is undefined, and the tenancy/auth requirement present in the schema is never surfaced in prose.

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 57%, so the schema already documents many parameters, and the description adds real meaning for the two configuration parameters by explaining they are fixed at first use and that conflicting values are refused. It also explains requestId's intent is retry-safe deduplication. It does not explain the op enum (peek is never mentioned), the bucket naming semantics, or the tenantId requirement, leaving roughly half the surface to the schema alone.

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 concrete framing (a single rate limiter shared across a fleet) and names the core operation and its return contract: take(cost) atomically spends tokens and returns allowed plus remaining, or refuses with retryAfterMs. That is specific verb+resource and an agent could act on it without opening the schema. It stops short of a 5 because no sibling tool is named or excluded, so the boundary against adjacent rate-limit style tools is left implicit.

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 strongly implied: use this when multiple agents must share one upstream rate limit, and the description explains that a mismatched capacity/refillPerSecond call is refused so fleets cannot disagree. It also advises sending a requestId on retryable mutations. However, there is no explicit when-not guidance, no statement of which operation (take vs peek) fits which situation, and no named alternative.

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