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

No annotations are supplied, so the description carries the full behavioral burden. It does add a useful commercial constraint ('5 free trial calls per signed wallet'), implying authentication by signed wallet and a call quota, but it says nothing about whether the result is a single scalar or a full EMA series, how many output points come back, or whether input ordering matters.

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 compact sentences with the definition and inputs front-loaded, no repetition. The trailing free-trial banner is promotional rather than descriptive, but it is short and carries real information about quotas.

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 two-parameter, annotation-free calculation tool with no output schema, the description covers the core intent and the period default. It falls short on input encoding, output shape, and any indication of how it differs from the many sibling moving-average tools, which is what an agent actually needs to route 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 description coverage is 0%, so the description must compensate, and it does partially: it identifies the meaning of 'values' (a price series) and supplies the missing default for 'period' (14). It still omits the format of 'values' (the schema types both parameters as strings, so the delimiter/encoding of the array is unclear) and any valid range for 'period'.

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 named resource ('Exponential Moving Average (EMA) of a price series'), which an agent can map directly to the function. It does not distinguish itself from close siblings such as x402-sma, x402-moving-average, or x402-exponential-smoothing, so the agent has to infer the difference from the 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?

There is no explicit statement of when to choose EMA over the many sibling averaging tools, nor any prerequisite or exclusion. The only usage-ish content is the imperative 'Provide values array and optional period', which describes input rather than selection criteria.

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