engineering.series_reliability

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

Annotations already cover read-only/idempotent/closed-world safety, but the description adds genuinely non-obvious behavior: inputs must be finite, the result is computed at 50 significant digits with HALF_EVEN and is independent of the caller's Decimal context. It does not describe error behavior for out-of-range values, keeping it at 4.

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?

Four sentences, front-loaded with the formula, then input format, then the independence caveat, then numeric precision. Every sentence adds information an agent would otherwise have to guess, with no repetition of the name or title.

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?

An output schema exists, so return values need not be explained; what remains — the input contract, the modeling assumption, and the numeric determinism — is all stated. Nothing needed to call this correctly is missing.

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 0%, so the description must carry the parameter — and it does: the argument is a list of numeric strings, at least one entry, each in [0, 1], expressed as a decimal rather than a percentage. That fully compensates for the bare schema.

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 description gives a specific verb and resource plus the exact formula (R_sys = ΠR_i), which in practice separates it from engineering.parallel_reliability and the exponential/Weibull variants. It stops short of naming an alternative tool explicitly, so 4 rather than 5.

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?

It states a clear applicability boundary — valid only when component failures are independent, not when failures are correlated — and gives input-format guidance (decimal 0.99, not percent 99). No sibling tool is named as the alternative for the correlated-failure case, so the routing guidance is incomplete but the context is clear.

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