9router models

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

The description ('List...') is consistent with readOnlyHint=true and openWorldHint=false, so there is no contradiction. However, it adds no behavioral context beyond what the annotations already convey: it does not clarify what kind of data is returned, whether the list is static or reflects live provider availability, or how it relates to the closed-world annotation.

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 a single six-word sentence with the verb front-loaded and zero filler. It is appropriately brief for a parameterless read-only tool, though the extreme terseness is partly responsible for the ambiguity in the resource terminology.

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?

Structurally the tool is simple — no parameters, read-only annotations, and an output schema that presumably documents the return shape, so the description need not explain return values. The real completeness gap is selection: an agent cannot reliably distinguish nine_models from nine_combos and nine_providers based on this description.

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?

With 0 parameters, the schema requires no documentation and the baseline is 4. The description adds marginal value by hinting at the output domain (routable combos + provider models), which is the only semantically relevant content for a parameterless tool.

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 uses a specific verb ('List') and names a resource ('routable combos + provider models'), so it is not a tautology. However, the resource terms are undefined jargon, and with sibling tools named nine_combos and nine_providers, the description does nothing to clarify how nine_models differs from 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?

There is no guidance on when to use this tool versus its closely related siblings (nine_combos, nine_providers, nine_usage). Given that an agent must choose among several nine_* listing tools, the absence of any selection criteria or exclusions is a notable gap.

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