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

With no annotations provided, the description carries the full burden of behavioral disclosure. It mentions the required input shape but does not disclose what the MACD calculation returns (MACD line, signal line, histogram), default period values (typically 12/26/9), or behavior with insufficient data. Critically, the instruction to 'Provide values array and optional fast/slow/signal periods' is contradicted by the input schema, which defines zero properties — an agent following the description cannot invoke the tool as documented.

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?

The description is compact at two sentences with no filler. The 'Macd:' prefix is mildly redundant with the tool name, but the rest of the first sentence earns its place by expanding the acronym, and the second sentence conveys the essential input expectation. Minor redundancy prevents a 5.

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 no output schema and no annotations, the description must explain return structure and call semantics, and it does not. An agent is left without knowing what the result contains (MACD line vs. signal vs. histogram), default periods, or the fact that the schema cannot accept the documented inputs. For a financial tool with this much unstated behavior, the definition is materially incomplete.

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?

The schema is empty, so the description is the only source of parameter information, and it does name the expected inputs: a values array plus optional fast/slow/signal periods. However, it provides no types, formats, defaults, or ordering, and the schema has no properties to accept these arguments. The description adds meaning beyond the empty schema but does so in a way that is inconsistent with the schema, misleading an agent about what it can actually pass.

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 states a specific verb and resource: 'Calculate the MACD (Moving Average Convergence Divergence) indicator.' This clearly identifies what the tool does and the acronym expansion adds precision. It distinguishes the tool from sibling indicators (x402-ema, x402-sma, x402-rsi) by naming the exact indicator, though it does not explicitly contrast with them.

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?

No guidance is given on when to use MACD versus sibling technical indicators like x402-ema, x402-sma, x402-rsi, x402-bollinger-bands, or x402-atr. The only instruction, 'Provide values array and optional fast/slow/signal periods,' is an invocation hint, not a usage-selection guideline. An agent has no basis to decide between this and its many indicator siblings.

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