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

With no annotations, the description carries the full burden and does so well: it defines the returned structure (blended series, per-venue series, volume, key_moves buckets at >=5 point moves) and discloses the cost model ($0.05 via x402, HTTP GET). It omits pagination, maximum retrievable range, and rate limits, which keeps it from a 5.

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?

Well front-loaded: the core purpose leads, then output contents, then usage hint, with the HTTP/cost/docs footer bracketed separately. Dense but every sentence carries information; the parenthetical per-venue qualifier is slightly hedged but not 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?

For a 4-parameter tool with no output schema and no annotations, the description conveys return shape, key_moves semantics, resolution options, and cost. The only real gap is the unexplained from/to date range, which an agent would need to set 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?

Schema description coverage is 0%, so the description should compensate. It explains granularity ('hourly or daily') and implies slug ('for a market'), but the 'from' and 'to' date parameters are never mentioned, leaving half the parameters undocumented anywhere. This is a partial compensation, warranting the baseline 3.

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: 'Probability time series for a market with key-move detection', then immediately specifies the resolution ('hourly or daily blended probability series') and the payload ('volume, plus key_moves'). This is distinguishable from siblings like probability_get (realtime) and the various probability_movers/board tools without opening any schema.

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?

Provides clear context: 'Useful for charting and for change-point context before paying for realtime reads', which implicitly routes the agent toward this instead of the realtime read tool. It stops short of an explicit when-not or a named alternative tool, so it is strong but not fully prescriptive.

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