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

Annotations only declare read-only/open-world/non-idempotent; the description adds the material facts an agent actually needs — exact price, dual payment rails, that an unpaid call errors with a structured x402 PaymentRequired object containing a fresh invoiceId, and that failed unpaid calls cost nothing. The fresh-invoiceId-per-call detail also coherently explains the idempotentHint=false annotation.

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?

Cost and payment rails are front-loaded, followed by the payload contents and the retry mechanics, so an agent reading only the first sentence already knows the price. A few clauses are dense and slightly awkward ('returns isError with the x402 PaymentRequired object'), but 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?

With no output schema, the description carries the return-value burden and does so by listing the template's sections. Price, error behavior, retry path, and payload shape are all covered for a single-optional-parameter paid 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?

Only one optional parameter exists and the schema already documents it at 100% coverage, so the baseline is 3. The description goes beyond the schema by stating that _meta["x402/payment"] is the preferred channel and payment_signature is the fallback for hosts that cannot set that meta key, giving the agent the ordering rationale.

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 names a specific resource — a blank two-way inter-consideration ledger template from FIM 2026 — and enumerates its contents (raw parties, per-duty owed items with open/met/unmet status fields, adjustment slots). That is far more specific than the title alone. It stops short of distinguishing itself from the sibling get_fim2026_schema, so an agent must infer which of the two FIM 2026 tools returns the template versus 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 payment protocol is spelled out well: first call without payment returns a PaymentRequired object with a fresh invoiceId, then retry with the signed payload. But there is no guidance on when to choose this tool over get_fim2026_schema or the other FIM 2026 siblings — usage is only implied by the framing question it claims to answer.

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