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

Annotations already cover safety (readOnly, idempotent, non-destructive). The description adds valuable context: cost ($0.001 USDC per successful call via x402 on Solana) and an alternative HTTPS endpoint, which are not in the annotations. It does not mention rate limits or error behavior, but the added cost and access details are substantive.

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 four sentences, front-loaded with the mathematical definition and formula, followed by an example, range, and pricing/endpoint. Every sentence contributes useful information, though the pricing/endpoint sentence, while important, could be considered slightly tangential to the core function.

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?

For a simple one-parameter math tool with annotations covering safety and no output schema, the description is nearly complete: it defines the computation, gives an equivalent formula, an example, the allowed range, and access details (cost, endpoint). The only missing piece is explicit usage guidance versus siblings, but that is a minor gap given the tool's simplicity.

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 0% schema description coverage, the description compensates by specifying that n runs from 1 to 1000000000000 and implying n is the upper bound of the sum. The example 'sum through 15 is 11' further clarifies the parameter's meaning. Minor gap: it does not explicitly say n must be an integer, though the schema handles that.

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 clearly states it computes the sum of ruler values v2(1) through v2(n), and provides an equivalent formula (n minus popcount) plus an example. It does not explicitly differentiate from siblings like ruler or ruler_prefix, so it stops 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?

The description gives no guidance on when to use this tool versus alternatives, nor does it mention any prerequisites or typical use cases. It only states the range and pricing, leaving the agent to infer usage.

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