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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds genuinely non-structured behavior: a $0.001 USDC per-successful-call charge via x402 on Solana, plus an equivalent HTTPS endpoint. That payment/auth context is exactly the kind of trait an agent needs and cannot get from the schema. It stops short of describing the return type or failure/refund behavior.

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?

Front-loaded with the definition, then compact examples, then the domain, then commercial/transport facts. Four short sentences, none 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?

With no output schema, the description still conveys the result indirectly ('takes 0', 'takes 11') and covers input domain, cost and transport. The only real gap is an explicit statement of the return type (a single non-negative integer count).

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 0%, so the description must carry the parameter — and it does: it establishes that n is the Collatz starting value, bounds it ('n runs from 1 to 100000', matching the schema min/max), and the examples show what different n values yield. Type and integer-ness are only implied.

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 defines the computed quantity precisely ('how many Collatz steps until the value is strictly below the start') and backs it with worked examples (1→0, 2→1, 6→1, 3→6, 7→11), so an agent can tell exactly what is being computed. It does not name or differentiate itself from the many near-synonym siblings (collatz_glide, collatz_steps, collatz_length), which is the only thing keeping it below 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 by the definition and the examples rather than stated: nothing says when to prefer this over collatz_glide or collatz_steps, nor are there exclusions. The price and alternate HTTPS endpoint give practical context but are not routing guidance.

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