list_models

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

With no annotations, the description carries the full disclosure burden, and it does useful work: it names the model source categories and clarifies that ordinary delegation resolves via the configured default, so the agent understands this call is informational rather than part of the delegation path. It stops short of describing the return shape (names vs. identifiers), which matters because the stated use case includes changing the default model.

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?

Two sentences, both load-bearing: the first defines what is listed, the second routes usage. The trigger and the exclusion are front-loaded before the explanatory clause, so an agent can act on the first read.

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-param listing tool with no output schema, the description covers what is enumerated and when to call it, which is nearly everything an agent needs. The one gap is that with no output schema, nothing states whether the returned models come back as display names or as identifiers accepted by set_delegate_config — relevant given the 'change the default model' use case.

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 there are no semantics to explain and the baseline of 4 applies. The description correctly refrains from inventing parameter guidance where none exists.

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 and resource ('List the models available for delegation') and then enumerates the three model categories returned (local/keyless, direct-API from opencode logins, agentic from the local install). This lets an agent distinguish it from ask_model and delegate without opening any schema.

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?

Gives an explicit positive trigger ('when the user asks what's available or wants to change the default model') and an explicit negative one ('not before an ordinary delegation'), plus the reason those cases differ. This is exactly the when/when-not/alternative structure the top score requires.

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