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

With no annotations, the description carries the full behavioral burden. It does disclose the scoping filter ('currently enabled', i.e. disabled rails excluded) and hints at return content ('public machine-readable contracts'), but says nothing about authentication, caching, or the actual response shape for what is presumably a safe read.

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?

A single front-loaded sentence with no filler; every phrase ('currently enabled', 'machine-readable contracts') contributes meaning.

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 zero-parameter, annotation-free read tool with no output schema, the description covers the essentials of what is listed and how it is scoped. It could say a bit more about the response format, but the gap is minor given the tool's simplicity.

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 tool takes zero parameters, so the schema needs no compensating description and the baseline of 4 applies. The description correctly adds no parameter detail because there is none to add.

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 gives a specific verb ('List') and resource ('currently enabled payment rails and their public machine-readable contracts'), so an agent can tell it apart from the product-oriented siblings. It stops short of explicitly contrasting itself with list_products or buy_product, so it earns a 4 rather than a 5.

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?

Usage is only implied: an agent needing payment options would call this, but the description never states when to use it, when not to, or how it relates to the sibling tools in the purchase flow. No explicit routing or prerequisites are given.

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