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

With no annotations, the description carries the full burden and does meaningful work: it discloses determinism ('no LLM'), latency (~30ms), a hard cost of $0.01 USDC per call on Base, and the payment channel in params._meta['x402/payment']. That payment prerequisite is exactly the kind of behavioral fact an agent needs before invoking. It stops short of describing failure modes or what a paid-but-failed call does.

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?

It is a single dense block with no wasted filler, and the capability list is front-loaded. However, cramming five capability domains plus pricing plus an HTTP endpoint into one sentence makes it harder to parse than a short purpose statement followed by a payment note would be.

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?

The advertised scope (datetime maths, cron expansion, entity extraction, schema validation) is far broader than the five-parameter conversion schema can express, with no explanation of how those modes are selected. With no output schema either, an agent has no way to know what a response looks like or which capability a given parameter set triggers.

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 all five parameters (value, from, to, round, values) are already documented in the schema itself. The description adds no parameter-level meaning beyond that, so the 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?

The description names concrete capabilities (unit/currency conversion, timezone maths, cron expansion, entity extraction, schema validation), but the tool is called 'extract' while its input schema only supports a single value/from/to/round conversion. An agent cannot tell which of the five advertised functions this call will actually perform, and the overlap with siblings agentkit__convert, agentkit__datetime and agentkit__validate is unaddressed.

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 statement of when to use this tool versus agentkit__convert, agentkit__datetime or agentkit__validate, despite those siblings covering the same advertised capabilities. The only conditional guidance is implicit in the schema ('omit to to get all equivalents'), which lives in the schema, not the description.

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