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

Annotations already declare readOnly, openWorld, idempotent, and non-destructive, so safety is covered. The description adds genuine context beyond that: it is a descriptive metadata call (channel catalog, client/server message shapes) and it clarifies the boundary that execution-authoritative data comes from other tools. Rate limits and output format are not mentioned, keeping it below 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?

The purpose is front-loaded in the opening clause, and the second sentence adds a meaningful scope boundary. The middle enumeration is dense but each listed lane earns its place; it is slightly long but not padded.

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, return values need not be explained, and the description adequately covers what the tool exposes and where it sits relative to execution tools. Given zero params and rich annotations, this is nearly complete; only the absence of explicit usage routing keeps it from a 5.

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 zero parameters, so per the rubric the baseline is 4. The description correctly implies a no-argument discovery call and does not introduce any misleading parameter expectations.

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 names a specific verb ('Describe') and resource ('canonical market-data lanes for agents'), then enumerates exactly which lanes are covered: public WebSocket, REST snapshot/quote/orderbook, consumer SSE, and control-plane WebSocket. It is clearly distinguishable from the discover_* siblings by its market-data-lane scope, though it never names a sibling explicitly.

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 closing sentence implies usage: quote and order-book tool calls are 'the execution-authoritative path,' so this tool is for understanding the realtime/display lanes rather than fetching data. That is useful implied routing, but there is no explicit 'use this when / not when' statement or named alternative.

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