model_config_set

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 the tool writes the "model" key in the OS API's Claude Code settings.json, that an empty string removes the key, and that changes take effect only on new sessions. It stops short of detailing permissions or whether existing sessions are unaffected, but the core mutation and timing behavior are clear.

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 compact and front-loaded: the primary purpose appears first, followed by the file-location detail and the empty-string removal behavior. Every sentence contributes useful information without redundancy.

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 one-parameter configuration setter with full schema coverage and an output schema, the description is complete enough. It covers the purpose, the write target, the removal behavior, and the delayed effect on new sessions, leaving no critical gap for an agent to call it correctly.

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 description coverage is 100% for the single required parameter, and the description mostly repeats what the schema already says about the empty string removing the key. The baseline of 3 is appropriate because the schema carries the parameter semantics and the description adds little beyond that.

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 states a specific verb and resource: set the default startup model for new CC sessions. It is clear and unambiguous, though it does not explicitly distinguish itself from the sibling model_config_get by naming the read operation as the alternative.

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 implies when this tool is relevant by noting it affects only NEW sessions and that an empty string restores CC's default. However, it does not explicitly state when to use this tool versus model_config_get or os_config_change, nor does it provide exclusions or prerequisites.

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