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

Goes well beyond the annotations: hard limits (three subscriptions, five seconds, 50 messages, 256 KiB), socket closure, no continuous feed or auto-reconnect, durable resume only for plays, and the instruction to report incomplete snapshot/replay and gaps. These are exactly the operational traits an agent needs and that readOnlyHint/idempotentHint cannot convey.

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?

Front-loaded with what is read, then constraints. Information-dense with no filler, though the middle sentences are long and run-on, which slightly hurts scannability. Every sentence carries load-bearing content.

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 complex streaming capture tool with an output schema available, the description covers the capability, entitlements, hard limits, termination behavior, and failure reporting. Return-value explanation is rightly omitted because an output schema exists. Only deep per-field subscription semantics remain thin, which is a minor gap.

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 0%, so the description must carry parameter meaning. It partially does: it maps subscriptions, the action verbs (snapshot, resync, usage, unsubscribe), resume-for-plays, and the limits that correspond to max_frames (50) and duration_ms (5000). However, the many nested subscription filter fields (event_ids, market_ids, participant_ids, sequences, etc.) get no explanation, leaving a substantial gap.

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 clear verb (Read) and resource (multiplexed WebSocket markets, scores, plays, stats, live game state, futures, hedge frames), enumerating the channel surface. This distinguishes it from siblings like capture_market_stream and capture_hedge_stream, though it never explicitly names those alternatives to sharpen the boundary.

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 concrete preconditions for use: per-channel entitlement, and for priced channels all periods, live/player-prop access and no delay. It also points to an alternative path ('Restricted custom plans can use REST') and notes stats needs a REST baseline. It stops short of naming a specific sibling tool to use instead.

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