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

Annotations already declare readOnly, idempotent, non-destructive, openWorld, so the safety profile is covered. The description adds a concrete operational constraint (5 qps rate limit) and clarifies the payload scope (exchanges plus whether transfers are supported), which is useful context beyond the annotations.

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 short lines, front-loaded with the core operation and ending with the rate limit. The first line is somewhat redundant with the second, costing a little efficiency, but nothing is wasted otherwise.

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 parameters and no output schema, this is a simple listing call, and the description covers scope, the transfer-support field, and the rate limit. Only a hint about return ordering or usage context 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?

The tool takes no parameters, so the baseline is 4. The description's mention of exchanges and transfer support implicitly describes the response shape rather than any call syntax, which is all that can be expected here.

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 ('Query stock spot supported exchanges') and adds the secondary dimension of transfer support, which is enough to distinguish it from siblings like cex_stock_query_stock_symbols or cex_stock_query_stock_fee_rate. It is clear, though the lead line 'Query supported exchanges' largely restates the tool name.

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?

There is no when-to-use, when-not-to-use, or alternative-tool guidance. The agent must infer from the name alone that this listing endpoint is the right one versus the other cex_stock_query_* tools.

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