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

Annotations only give generic safety hints, and the description adds genuinely load-bearing context: a per-call price, the x402 challenge/retry protocol, where to put the payment (_meta["x402/payment"]), and an HTTP equivalent endpoint. It does not cover rate limits or the shape of the returned digest, but the paid-invocation behavior—the main surprise for an agent—is fully disclosed.

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?

Three tight sentences: purpose first, then billing protocol, then the HTTP mapping. Every sentence carries information an agent needs before calling, with no filler.

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?

No output schema exists, so the description should say what comes back (a hex digest, its length/format), but it never does. The billing side is thorough while the result side is missing, leaving a real gap for a compute-style 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 coverage is nominally 100% but the sole parameter's description is just "string", so the schema conveys almost nothing; the description likewise never explains hashing semantics (encoding, byte handling, empty input). Baseline 3 applies since there is one parameter and the tool text does not contradict anything.

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 plus the exact algorithm ("Hash a text value with the MD5 algorithm"), which separates it from devutils_hash_sha256 on inspection. It stops short of explicitly contrasting the two hashes, so an agent must infer the choice from the algorithm name alone.

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?

Usage is only implied by the algorithm name; there is no statement of when to pick MD5 over the sibling devutils_hash_sha256, nor any warning that MD5 is unsuitable for security-sensitive use. The payment retry loop is explained, but that is invocation mechanics rather than selection guidance.

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