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 genuinely useful context beyond that: it clarifies this returns descriptive lane information rather than live data, and that quote/order-book tool calls remain authoritative for execution — a distinction an agent could otherwise get wrong.

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 sentences, front-loaded with the core purpose, and the scope list (query params, channel catalog, message shapes, SSE, control-plane) tells the agent what the output will cover. The parenthetical enumeration is dense but each item is informative rather than padding.

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 zero parameters, full annotation coverage, and an output schema that carries the return structure, the description needs only to establish purpose and scope — which it does. The one remaining gap is that it does not route the agent relative to the other discover_* tools.

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 the baseline is 4; there is no argument surface the description needs to explain. Nothing in the description misleads about inputs.

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 and resource: 'Describe the canonical market-data lanes' and enumerates the lanes covered (public WebSocket, REST snapshot/quote/orderbook, consumer SSE, control-plane WebSocket). It also distinguishes itself from the data-fetching siblings by noting that quote/order-book tool calls remain the execution-authoritative path, so an agent can tell this is documentation rather than a data call.

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 framing 'this describes the realtime/display lanes alongside them' implies the tool is for orientation before/alongside real data calls, but it never says explicitly when to call it versus kellian_discover_events, kellian_discover_webhooks, or kellian_list_capabilities. No when-not conditions or prerequisites are given, leaving routing to inference.

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