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

Annotations already declare read-only, idempotent and non-destructive, so the safety bar is low. The description still goes well beyond them: it discloses the hybrid mechanic (real results before replay_from are preserved, the remainder is Monte-Carlo simulated), the flip precondition ('must be a decided knockout tie before replay_from'), the iteration clamp of 100..20000, and seed-driven reproducibility.

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 one-sentence purpose, then Args, Returns and Examples in a scannable order with no filler prose. The Returns block is somewhat redundant given a real output schema exists, which keeps it from a 5, but every line is legible and purposeful.

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, zero-required simulation tool with annotations and an output schema, the description covers the simulation contract, flip constraints, reproducibility via seed, iteration bounds, and result shape — more than an agent needs to invoke it 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 coverage is 100%, so baseline is 3. The Args block largely restates the schema descriptions verbatim (replay_from stage meanings, flip_winner_of format, iterations clamping), adding little new semantics; the one genuinely additive detail is the 'any order' note on team ordering in flip_winner_of, which mirrors the schema anyway.

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 names a specific verb (replay) and resource (World Cup 2026 tournament) plus the distinctive what-if twist of flipping one knockout result, so an agent knows exactly what capability this is. It does not, however, contrast itself with close siblings such as football_simulate_bracket, football_simulate_group, or football_knockout_path, which is the only thing separating a 4 from a 5 here.

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 mechanics of when replay_from and flip_winner_of apply are explained in detail, and the two examples show realistic invocations. But there is no explicit routing guidance — nothing says to pick this over football_simulate_bracket when the agent wants a plain simulation, or over football_knockout_path when it just wants the real bracket.

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