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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description adds valuable behavioral context beyond the annotations: similarity is deterministic, based on surprise directions and distance, and results are historical observations only with no predictive or trading-recommendation value.

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 efficiently structured and front-loaded: the core function, usage guidance, deterministic method, limitation caveat, and supported scope each appear in separate, purposeful sentences. No filler or redundant restatement of the tool name or schema exists.

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?

Given a rich input schema, full schema coverage, annotations, and an output schema, the description fills the remaining gaps well. It explains the deterministic similarity logic, the supported instrument/event scope, and the non-predictive nature of results, so an agent has enough context to 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?

Schema description coverage is 100%, so the schema fully documents all four parameters and their defaults. The description reinforces the reference-period concept by mentioning 'selected or latest release', but it does not add meaningful parameter semantics beyond what the schema already provides.

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 first sentence states a specific action and resource: finding historical U.S. CPI releases with surprise profiles similar to a selected event and returning their deterministic EURUSD reaction statistics. This clearly differentiates the tool from siblings like get_historical_reaction_context or get_market_reaction by focusing on historical analogs and deterministic stats.

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 tells the agent when to use the tool: when the user asks how EURUSD reacted historically to similar CPI surprises, whether the initial reaction persisted, or whether the current reaction was unusual. It provides clear context but does not explicitly name alternatives or state when not to use it.

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