live_prices

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

Annotations already establish readOnlyHint=true, and the description reinforces this ('Read-only; single batch, no arguments') rather than contradicting it. It adds genuine behavioral context beyond annotations: the fixed-instrument scope and the null-field semantics when an upstream quote is unavailable. It stops short of stating freshness/latency guarantees, so not quite 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?

Purpose and routing constraint are front-loaded in the first paragraph, which is ideal. The trailing 'Returns' block enumerates every key and duplicates what the output schema already documents, making it the one part that doesn't fully earn its space.

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 zero-argument read-only tool this is complete: scope, sibling routing, read-only guarantee, batch behavior, and null handling are all covered, and an output schema exists to carry the return structure. Nothing an agent needs to call 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?

Zero parameters, so the baseline is 4. The description correctly states 'no arguments', which is consistent with the empty schema and leaves nothing ambiguous for the caller.

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 (Fetch) and a precise, enumerated resource (spot gold, USDCNY/AUDCNY FX, NDQ.AX, VIX, TNX) as a fixed reference set. It also explicitly distinguishes itself from the sibling `status`, which covers the user's own positions. An agent can route correctly without opening any 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?

Gives explicit when-to-use (quick market context before analysis; user asks 'how is the market / what's the gold price') and an explicit when-not, naming the alternative tool (`status`) for user-held positions with the condition that selects it. No inference required.

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