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

No annotations exist, so the description carries the full burden. It correctly implies a pure, deterministic computation with no side effects, but says nothing about input size limits, required integer format, or result range. The word 'efficiently' is marketing rather than behavioral disclosure.

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?

Two sentences, zero filler, with the operation and formula front-loaded. Tight and appropriately sized for a simple arithmetic tool.

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 simple deterministic math operation with 100% schema coverage and no output schema needed, this is nearly complete. A minor gap: the schema types are strings while the description says 'integers', which could confuse an agent about whether to pass numeric literals or string-encoded big integers.

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%, so the schema already documents base, exponent, and modulus individually. The description adds the formula tying the three together, which clarifies roles, but does not explain formats or constraints. 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 (Calculate) and resource (modular exponentiation) and even gives the mathematical form base^exponent mod modulus, which is unambiguous. It does not differentiate from adjacent siblings such as x402-multiplicative-inverse or x402-extended-gcd, so it falls short of a 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?

The description only tells the agent what arguments to supply, not when this tool is the right choice versus alternatives like multiplicative inverse or Euler's totient. No when-to-use or when-not-to-use context is provided.

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