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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, destructiveHint false, openWorldHint), but the description adds real value beyond them: the 50-match result cap, that it returns asset class/services/pricing tier, and explicitly that it never returns live prices or initiates payment. The payment/live-price caveat is exactly the kind of behavioral boundary an agent needs.

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 dense sentences with the free/read-only reassurance front-loaded alongside the action, and no filler or repetition.

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 an output schema present and annotations carrying the safety hints, the description only needs to frame purpose and key behavioral boundaries, which it does; the result cap, free/paid distinction, and no-payment guarantee round it out.

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%, so the schema already documents query and the asset_class enum with examples. The description's mention of asset classes loosely mirrors the enum but adds no syntax, format, or matching-behavior detail (e.g., how partial or ambiguous queries resolve), 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?

The description states a specific verb and resource: discover supported crypto, equity, FX, and metal symbols, with the result shape (up to 50 catalog matches). It is clearly distinguishable from data-fetching siblings like fetch or get_market_data_endpoint, though it never explicitly contrasts itself with list_instruments or get_product_catalog, which overlap in resource.

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?

It gives clear usage context: run this before hitting the paid HTTP API, and it is free, so an agent knows this is the cheap discovery step. It stops short of exclusions or naming alternatives, which keeps it from a 5.

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