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

Annotations only give generic hints (readOnlyHint=false, openWorldHint=true, idempotentHint=false); the description adds genuinely valuable behavior beyond them: a $0.005 per-call price, USDC-on-Solana payment channel, and the exact two-step x402 handshake including the _meta["x402/payment"] retry key. It does not explain why the operation is flagged non-read-only or how long a simulation run takes, so it stops short of a 5.

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?

Two tight sentences with the purpose front-loaded before the payment logistics. The billing/protocol detail is long but earns its place for a paid tool; nothing is 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?

There is no output schema, yet the description says nothing about what a simulation returns (projected income stream, distribution schedule, yield figures), nor what 'distribution flywheel' concretely means versus the linear projection. Payment mechanics are fully covered, but the result shape remains a gap for a paid compute tool.

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 100% — each of reinvest, allocations, and horizon_years is already documented with defaults and accepted holding shapes. The description adds no parameter meaning on top of that, so the baseline 3 applies.

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?

Specific verb plus resource: 'Simulate an income portfolio and its distribution flywheel'. This is clearly distinguishable from the sibling etf_distributions, though the description never explicitly names that sibling as the raw-data alternative. An agent can tell what the tool does without opening the schema.

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 detailed invocation mechanics (pay-and-retry challenge flow, HTTP fallback endpoint) but no guidance on when to use this versus etf_distributions or when a user should simulate rather than query actual distributions. Usage context is only implied by the tool's purpose.

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