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

With no annotations, the description carries the behavioral burden and does add real context: cost ($0.04 via x402), the exact HTTP endpoint (GET /v1/movers/politics-world), and the ranking/volume-surge semantics. It does not disclose auth prerequisites beyond x402, rate limits, or return field details, so it is helpful but not exhaustive.

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-loads the core purpose in the first sentence, then adds usage and scoping context. The bracketed endpoint/price/docs line is dense but earns its place by carrying the pricing and protocol information the schema omits. Minimal waste overall.

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 4-param read tool with no output schema and no annotations, the description supplies the missing operational context (pricing, protocol, endpoint, output shape reference). It never enumerates the returned fields or pagination, but 'same shape as /v1/movers' gives the agent a usable return-format pointer.

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 only 25% (only min_liquidity documented in the schema), so the description should compensate more than it does. It clarifies the window values (1h/6h/24h) and that the window is user-chosen, but leaves limit, category, and min_liquidity semantics largely to the schema, so it adds only partial value.

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+resource (world politics probability moves) with scope qualifiers: ranked by absolute probability change, active markets, chosen window. It distinguishes itself from siblings by being 'pre-filtered to world politics markets', differentiating it from probability_movers_politics-us and the base probability_movers.

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 fastest way to see where news is landing in world politics' gives clear context for when to reach for it, and 'Same shape as /v1/movers, pre-filtered' points at the base tool as the alternative. However, it never explicitly states when NOT to use it or names the politics-us sibling as the contrasting choice, so it falls short of full when/when-not routing.

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