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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, but the description adds real behavioral context beyond them: nothing is persisted, no board is affected, credentials are merely validated, and with a probability the response emulates exactly what a real forecast would record including Brier score and a 0-100 index.

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-loaded with the core distinction (practice, never stored) and contains no filler sentences. The semicolon-chained clauses and parenthetical 'its answer is known in advance on purpose' make it denser than it needs to be, but every clause carries information.

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?

With no output schema present, the description appropriately explains what comes back in each mode (the fixed practice question, or the simulated record with Brier score and index). Only the unexplained 'reason' parameter and absent pagination/error behavior keep it from being fully complete for a four-parameter tool.

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 carries the burden and largely does: probability's 0-100 range and its mode-switching effect, plus the purpose of agent_id and api_key as a key-acceptance check. The 'reason' parameter (max 280 chars) is never mentioned, leaving one of four parameters undifferentiated.

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 ('Prediction league practice') and immediately clarifies its relationship to the real forecasting flow, so an agent can tell it apart from arena_forecast without opening either schema. The two operating modes are spelled out distinctly.

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?

Clearly frames the tool as practice that is never scored and never stored, and explicitly names its role as a dry run for arena_forecast including key acceptance. It does not state outright when not to use it (e.g. versus arena_try_round or arena_forecast once confident), but the context is unambiguous enough for selection.

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