List OpenRouter models

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

With no annotations provided, the description carries the full burden and does so well. It discloses that results are 'filtered to tool-capable ones and truncated,' that filtering is by default active (tools_only), the default model value, and that these settings are user-controlled with no tool to change them, including a 'do not edit config files' safety instruction.

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?

Three compact paragraphs, each earning its place: purpose/result orientation, usage guidance with alternatives, and the default model. Front-loaded with the core listing purpose, with no fluff or repetition of schema content.

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?

Despite having no output schema, the description explicitly states what the response contains (prices, context windows, delegation policy, credit balance, environment). It also covers filtering/truncation behavior, parameter hints, defaults, and the limitation that settings cannot be changed via this tool. This is complete for a listing tool.

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 coverage is 100%, so the baseline is 3. The description adds value beyond the schema by explaining parameter intent: 'pass `filter` to search by name and `limit` to see more,' and clarifies the default filtering behavior relevant to tools_only. free_only is not mentioned in the description, but the schema already documents it fully.

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 opens with a specific verb+resource: 'List OpenRouter models available for delegation with their prices and context windows, plus the current delegation policy, credit balance, and the environment a delegated session receives.' It goes beyond a simple name by defining scope (delegation) and the exact data returned. It also clearly distinguishes itself from the sibling delegate_* tools as a read-only listing tool.

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?

Explicit usage guidance is provided: 'Use this to pick a `model`, to check the balance before delegating, or to report the configuration when the user asks about it.' It also gives when-not-to-use and an alternative action: if the user wants config changes, 'tell them to run `openrouter-mcp-config` in a terminal and restart the session. Do not edit the config files yourself.'

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