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

Beyond the readOnly/openWorld/idempotent annotations, the description discloses the paid-call model (0.01 RLUSD on XRPL or 0.01 USDC on Base), the exact failure behavior (isError plus an x402 PaymentRequired object with a fresh invoiceId), the retry path via _meta['x402/payment'] or payment_signature, and that unpaid calls are free. That is precisely the behavioral context annotations cannot express.

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?

Pricing is front-loaded, then purpose, then error/retry behavior, then the free-when-unpaid reassurance—a sensible order with little waste. It is dense and slightly repetitive on payment mechanics, but every sentence carries information.

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 and a single optional parameter, the description still covers what is returned (duty definitions, self-checks, indicators, with the 'not legal advice' caveat) and the exact error shape on non-payment. Nothing an agent needs to invoke it correctly is missing.

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 100% and the single parameter is already documented, so the baseline would be 3. The description adds real meaning by explaining why the parameter exists (hosts that cannot set _meta) and the expect-to-omit-on-first-call workflow, which is more than the schema conveys.

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 the specific verb and resource: it returns the FIM 2026 guidance schema, namely 'raw duty definitions, self-checks, and measurable indicators.' It even frames the single question the tool answers, which is unusually concrete. It does not differentiate against the sibling get_fim2026_ledger_template, so it stops 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?

Usage is implied by the question the tool 'solves,' and the payment-retry flow is spelled out, but there is no explicit when-to-use/when-not guidance and no mention of the closely related get_fim2026_ledger_template sibling. An agent must infer the boundary from the name alone.

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