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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds that results are windowed ('the window's', 'due next') and that it bundles multiple datasets, but it says nothing about latency, caching, coverage limits, or freshness beyond the window — modest added context over structured fields.

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 snapshot summary followed by the use case. The first sentence is a dense enumeration but every clause maps to a distinct returned data category, so little is wasteful.

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, the description needn't detail return values, and annotations cover safety. It successfully conveys the composite nature and intended cadence; the only missing piece is guidance on choosing this over the narrower siblings, which is a minor gap for a zero-required-parameter tool.

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 coverage is 100% and both parameters carry inline descriptions with ranges and defaults, so the baseline is 3. The description only implicitly gestures at the two windows ('the window's', 'due next') without adding format or tuning guidance beyond the schema.

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?

Opens with a concrete verb-and-resource framing ('A market snapshot in one call') and enumerates exactly the contents: headlines, price moves around news, econ data actual vs forecast, earnings, and published investigations of sudden moves. That enumeration distinguishes it from focused siblings like top_movers, economic_data, and earnings by establishing it as the aggregated view.

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?

Explicitly names the triggering intents: 'what's moving markets right now', a pre-market check, or an hourly check. It gives clear positive context but never states when to prefer the narrower siblings (top_movers, ticker_brief, watchlist_digest) instead, so the routing boundary is left to inference.

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