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

Annotations already declare readOnlyHint=true, so the read-only nature is covered. The description adds valuable context beyond that: it discloses a per-call cost (0.03 USDC over x402) and a terms link, plus a professional-use restriction. These are behavioral or operational traits not captured by the annotations. It does not contradict the annotations or introduce ambiguous behaviors, so a 4 is appropriate.

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?

The description is longer than minimal but each sentence earns its place: the primary purpose is front-loaded, followed by methodological details, data features, restrictions, and finally pricing/terms. It is well-organized and not redundant, though it could be slightly more compact by merging some clauses. Overall, it is structured effectively without being bloated.

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?

For a data retrieval tool with no output schema, the description provides a solid overview of what the response will contain: rows with observations, sources, dates, issuer figures, differences, and explicit handling of unavailable/quoted rows. It also notes coverage lists and gaps. It does not specify the exact response structure, but it conveys the semantic content well enough for an agent to understand the return. The addition of cost and terms further completes the operational context.

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?

The schema has 100% description coverage for the only parameter ('instruments'), fully documenting the comma-separated format and default behavior. The tool description itself adds no further parameter detail, but since the schema already handles it, the baseline of 3 is correct. The description does not need to repeat what the schema already provides.

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 a specific verb-resource pair: 'Realised 30-day yields' for tokenized treasury funds, and names the specific universe (13 funds under the Open Treasury Yield Basis). It also details what measurements include (NAV, price, balances) and what is explicit (quoted/unavailable rows). This clearly distinguishes it from siblings like get_rwa_history or get_rwa_instrument, which pertain to historical or single-instrument data.

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 does not provide any explicit guidance on when to use this tool versus alternatives. It mentions a business/professional use restriction and terms, but nothing about selecting it over siblings. There is no statement like 'use this for current yields' or 'for historical data use get_rwa_history'. The only implied context is the tool's own name and content, but no exclusions or alternatives are mentioned.

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