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

Annotations already declare readOnly, idempotent, and non-destructive hints, so the description does not need to repeat safety traits. It adds value by detailing the call's behavior: it returns a composite of risk regime, whale flows, unusual coins, movers, and forced-close picture, and explicitly notes perp/lending are kept separate. A minor gap is not specifying the exact recency window, but the output schema likely covers return details.

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 description is two sentences with no wasted words. The first sentence front-loads the core promise and content list; the second effectively differentiates the tool from market_digest. Every element earns its place and the length is appropriate for the complexity.

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 no-parameter tool with an output schema, the description fully covers purpose, scope, and positioning among many sibling tools. The only minor ambiguity is the vague time window ('recently'), which is likely intentional for an on-demand brief but could be tightened. Overall it is complete enough for an agent to select and invoke the tool correctly.

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 has zero parameters and schema coverage is 100%, so there are no parameter ambiguities to resolve. The description instead lists the informational content of the call, which is all that is needed. It deliberately conveys no extra parameter detail because none exists.

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 opens with a clear verb+resource framing ('What changed across the market recently, in one call') and enumerates the specific data categories covered. It also distinguishes itself from sibling market_digest by framing the use case as on-demand versus timer-driven, which sets it apart from other market brief tools.

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 description explicitly names market_digest as the same one-call brief intended for a timer, positioning market_changes for on-demand questions like 'what changed since this morning / overnight.' It also states 'Descriptive market data only,' giving the agent clear expectations about scope without needing to infer.

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