Update pull request description

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

With no annotations, the description carries the full burden of behavioral disclosure. It accurately states the mutation ('Replaces') and explicitly lists what remains unchanged, which is critical for a partial update. It does not discuss permissions or response contents, but the behavior is simple and well-covered.

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 a single, front-loaded sentence that states the primary action and key boundary in one breath. Every word earns its place; there is no redundancy or filler.

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 simple single-field update with no output schema, the description adequately covers the core purpose and scope. It would benefit from mentioning that the old description is irrevocably replaced (though 'replaces' implies this) and any prerequisite like the PR existing, but these are implicit. The description is complete enough for the tool's simplicity.

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 all 4 parameters, so the schema already documents each field. The description adds context by explaining the effect on the existing description and clarifying that other PR fields are untouched, but it does not provide additional parameter-level syntax or format details beyond the schema. Baseline 3 is appropriate.

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 uses a specific verb ('Replaces') and resource ('pull request's description'), and clearly distinguishes from sibling tools like bb_update_pull_request by scoping only to the description field. It explicitly states what it does not affect (title, reviewers, destination branch), making it unambiguous.

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: when only the description needs updating, not other PR attributes. It provides clear exclusions ('without touching its title, reviewers or destination branch'), though it does not name alternative tools like bb_update_pull_request explicitly. Still, the guidance is stronger than average.

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