Create a T3 thread

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

Annotations are minimal (readOnlyHint false, destructiveHint false), so the description carries the burden. It discloses that the operation may not be immediately accepted ('check the mutation status for acceptance') and that the returned branch and worktree reflect the request, indicating asynchronous behavior. This adds value beyond annotations, though it doesn't detail failure modes or retry logic.

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 short sentences, each adding value. The purpose is front-loaded, the conditional for modelSelection is precise, and the behavioral note about mutation status is concise. No filler or redundancy. Excellent structure.

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 an output schema, the description omits explanations for most parameters, prerequisites (e.g., project must exist), and the meaning of runtimeMode and interactionMode. With 8 parameters, nested objects, and low schema coverage, the description is not complete enough for an agent to use it correctly without additional context.

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 0%, so the description must compensate for all 8 parameters. It only explains when to supply modelSelection (when the project has no default). It does not clarify title, projectId, idempotencyKey, branch, worktreePath, runtimeMode, or interactionMode. The hint about branch/worktree is vague. This is insufficient given the parameter count and complexity.

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 clearly states the verb 'create', the resource 'thread', and the context 'in an existing T3 project'. This distinguishes it from sibling tools like t3_thread_get or t3_thread_send, which operate on existing threads. The mention of modelSelection also hints at a specific condition, adding clarity.

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 to use this tool (to create a thread) and provides a parameter condition ('Supply modelSelection when the project has no default'), but it does not explicitly name alternatives or state exclusions. It doesn't say 'use this instead of X' or when not to use it. The context is clear but not fully explicit.

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