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

Annotations already indicate this is a mutating, non-destructive operation(?). The description adds valuable behavioral detail: the required authenticated write access, the base_branch default behavior, and the return shape {number, url}. This goes beyond what annotations and schema provide.

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 carrying necessary information: the action, the key parameter behavior, and the auth/return contract. No filler or repetition.

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?

The description covers the core requirements, auth prerequisite, default branch behavior, and return format, which is complete enough for a tool with no output schema. It could add a brief note distinguishing from open_draft_pr, but that is more of a selection aid than a calling requirement.

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 all parameters already have descriptions. The description largely repeats schema details like head_branch being required and base_branch defaulting to the repo default branch witout adding new semantic information beyond the schema.

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: 'Open a new pull request.' It is clear and actionable. However, it does not explicitly differentiate from the sibling tool open_draft_pr, so an agent must infer that this tool is for non-draft PRs.

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 useful prerequisites: head_branch is required, base_branch has a default, and the caller needs write access. It does not explicitly compare to alternatives like open_draft_pr or merge_pr, so usage guidance is implied rather than explicit.

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