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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and a closed-world profile, so the safety story is fully covered. The description adds the deterministic formula and that it returns remaining quantity, which is useful, but says nothing about unit handling or edge cases (time=0, half_life at the 0.001 floor).

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 purpose, then formula, inputs, return, and a cross-reference in a compact run of sentences. The formula earns its place; the list_bundles pointer is marginally useful and slightly dilutes an otherwise tight definition.

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 an output schema present the description need not explain the return value, and annotations cover the safety profile, so the essentials are in place. The one real gap is unit consistency between half_life and time, which matters for a physics calculator and is never mentioned.

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% and all three parameters are documented in the schema, so the schema carries the parameter burden. The description only restates the inputs ('initial qty, half-life, elapsed time') without adding format or unit guidance beyond what the schema already says, so baseline 3 applies.

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 ('Compute remaining quantity after radioactive decay') and goes further by giving the exact formula N=N0·(0.5)^(t/half-life), which pins down the semantics unambiguously. An agent can distinguish this from neighbours like calculate_caffeine_half_life because the domain (physics/carbon dating) is named.

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?

'Use for physics or carbon dating' gives a loose context but no when-not conditions or a named alternative for the same task. The pointer to list_bundles is a discovery hint rather than guidance on choosing between competing calculators, so usage is only implied.

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