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

Annotations already declare readOnly, idempotent, non-destructive, openWorld, so the safety profile is covered. The description adds genuinely non-derivable operational context: it is a paid call at $0.001 USDC per successful call via x402 on Solana, and the same operation is reachable over HTTPS at a stated endpoint — exactly the kind of cost/transport detail an agent needs before invoking.

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?

Front-loaded with the definition, then a concrete example, then payment/transport facts — a sensible order with no fluff. The endpoint URL is long but is real operational information rather than waste.

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 small two-parameter math tool with no output schema, the description does say what is returned (a tangent vector) and illustrates the output format with (3/2, 0). It still leaves the input formats of 't' and each point undefined, which is the main call-time risk.

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 carries the burden, yet neither parameter is explained. 'points' is only hinted at by the example (four control points of an arch) with no statement about point format, ordering, or quadratic-vs-cubic cardinality; 't' is never described, and its string type with maxLength 40 (likely a fraction or decimal such as '1/2') is left entirely ambiguous.

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+resource: the tangent vector of a quadratic or cubic Bezier at t, clarified as the derivative curve evaluated at t. That is much better than a tautology. However, it never distinguishes itself from the very similar sibling bezier_derivative (nor from bezier_quadratic/bezier_cubic), so an agent must guess which of the two near-identical derivative tools to pick.

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 worked example (arch at one half has tangent (3/2, 0)) implicitly tells the agent when the tool is appropriate and what to expect. There is no explicit when-to-use/when-not guidance and no mention of bezier_derivative as the alternative, so routing must be inferred.

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