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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior. The description adds valuable behavioral context not covered by annotations: pricing ($0.001 per successful call via x402 on Solana) and an alternate HTTPS endpoint, which is critical for an agent to know before invoking.

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 front-loaded with the core operation and examples, followed by the input range and payment details. It is efficient with no wasted words, though the pricing and endpoint sentences could be slightly more compact.

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, single-parameter mathematical tool with no output schema, the description covers the operation, examples, input range, cost, and an alternate endpoint. It does not explicitly state the return type (an integer count), but this is strongly implied by 'How many 1 digits...'.

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. It states that n ranges from 0 to 999999999999 and provides four illustrative examples that clarify what n represents, but it does not explicitly define the parameter or add syntax details beyond what the schema already specifies with min/max.

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 states a specific operation: counting the number of 1 digits in the base -2 representation of n, with clarifying examples (0→0, 1→1, 6→3, 7→4). It does not explicitly differentiate from sibling tools like negabinary or negabinary_len, 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?

The description gives no guidance on when to use this tool versus the many sibling tools (e.g., negabinary, negabinary_len, negabinary_digit). It only states the input range and pricing, leaving the agent to infer the appropriate context.

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