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 real context beyond that: the data provenance is a walk-forward record and each result carries sample sizes and confidence intervals, which tells the agent the numbers come with statistical reliability measures. It does not mention pagination, latency, or the horizon enumeration, which keeps it short of 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?

One dense sentence with the resource front-loaded and no filler words; every clause (rates, granularity, sample sizes, confidence intervals, provenance) carries information. It could be slightly clearer if the output-grained nature of 'horizon' were signposted, but nothing is wasted.

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 one-parameter, read-only tool with no output schema, the description explains both the nature of the values (reach rates) and their statistical framing (sample sizes, confidence intervals, walk-forward source), which is enough for correct invocation. The remaining gap is that the set of horizons and the symbol universe (see list_symbols) are left implicit.

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% with the single 'symbol' parameter documented with an example ('ETHUSDT'), so the schema already does the work and baseline 3 applies. The description introduces 'horizon' as a dimension, which is not a callable parameter — the agent may look for a horizon argument that does not exist. That mild ambiguity offsets the added grouping context.

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: 'Returns historical band reach rates by symbol and horizon', plus the resolution of the data ('with sample sizes and confidence intervals'). This is clearly distinct from siblings like get_magnet_levels_teaser or hk_levels, which concern levels rather than historical reach rates. The only softness is that 'band reach' and 'horizon' are domain terms not defined anywhere in the definition.

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?

There is no when-to-use or when-not-to-use guidance and no named alternative. The 'walk forward record' phrasing hints this is backtested/historical rather than live, but the agent must infer that distinction itself rather than being routed anywhere, e.g. to get_engine_read or get_decision_packet for live state.

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