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

No annotations provided and description provides no behavioral detail, edge cases, or mention of how substrings are located or returned. The name implies string extraction but no specifics; no annotation contradiction.

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?

Single sentence but entirely redundant with the tool name; this is under-specification rather than purposeful conciseness.

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 params, no output schema, and no annotations, a name-only description leaves numerous questions: how are 'between' bounds specified? What is the output? What edge cases/errors? At least the zero-parameter schema makes invocation trivial, but the tool cannot be used meaningfully for safe selection.

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 input schema has zero parameters, so schema coverage is trivially 100%; with no parameters to document, the description isn't required to add parameter semantics, and the baseline 4 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?

Description simply repeats 'Substring Between' after the name/title, a near-tautology. It doesn't specify what it does with substring inputs, what between means, or how it differs from x402-substring-after and x402-substring-before.

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 on when to use this tool rather than the tightly related siblings (x402-substring-after/x402-substring-before) or string tools in general.

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