Set the default model

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

Annotations already indicate readOnlyHint=false and idempotentHint=true. The description adds meaningful behavioral context by disclosing that the choice is persisted to the config file and applies to future runs, making the side effect concrete.

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 short sentences plus an example, with no filler. The core behavior is front-loaded and the parameter format is explained immediately after.

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 single-parameter configuration tool, the description covers the purpose, the effect, the persistence behavior, and the parameter format. There is an output schema, so return-value documentation is not needed here.

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 schema only says 'model' is a string with 0% description coverage. The description compensates fully by defining the expected format as a 'provider:model' spec or alias and giving a concrete example ('example:flux-schnell').

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 ('Persist') and resource (the default model), and explicitly ties it to generate_image calls made without a model argument. This clearly differentiates it from sibling tools like list_models or add_provider.

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?

The description gives clear context: use this tool to set the model that generate_image will fall back to when no model is provided. It does not explicitly list when not to use it or name alternatives, but the scoped usage is evident.

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