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

Annotations already declare readOnly, idempotent, non-destructive, and openWorld. The description adds meaningful behavior beyond that: output switches to a decimal string beyond 15 digits, indexes are bounded 0–4096, and each successful call costs $0.001 USDC via x402.

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-loads the core operation and constraint, then adds example, output-format note, price, and alternate HTTPS endpoint. Slightly dense with payment/transport details, but every sentence provides actionable context for an agent.

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 steps in to explain the return type shift to a decimal string past 15 digits. It also covers input bounds, ordering constraint, cost, and alternate endpoint, leaving little ambiguity for invocation.

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 parameter meaning. It successfully defines lo and hi as inclusive index bounds, states lo must not exceed hi, and reiterates the 0–4096 range, fully compensating for the bare schema.

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?

States a specific verb and resource: 'The sum of Tetranacci numbers from lo through hi inclusive.' The range scope clearly separates it from siblings like tetranacci (single term) and tetranacci_mod, but it does not explicitly name those alternatives.

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?

Provides a key constraint ('lo must not pass hi') and an illustrative example (T0 through T10 is 116), which implies correct usage. However, it never states when to prefer this over tetranacci, tetranacci_index, or tetranacci_mod, leaving alternative selection to inference.

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