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

Goes well beyond the annotations (readOnlyHint=false, destructiveHint=false) by disclosing that no force-push occurs, that the new head is a merge commit subject to CI gates, that conflicts leave the branch unchanged, and that write access plus 'repo' scope are required. The full success and failure response shapes are spelled out, which is the behavioral detail an agent needs before calling a mutation tool.

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 action and its non-force-push framing come first, followed by conflict behavior, authorization, and return shape — a logical order with no filler. It is dense but multi-clause; a slightly tighter failure-shape sentence would make it leaner.

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?

There is no output schema, so the description supplies the return contract itself ({ok, status, headSha, previousHeadSha, baseSha, url} and the failure variant) plus auth requirements and failure semantics. For a three-parameter mutation tool, nothing an agent needs to invoke it correctly or interpret results is missing.

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%, so owner, repo, and number are already documented in the schema, and the description adds no per-parameter meaning such as format or validation rules. The baseline 3 applies when the schema carries parameter semantics on its own.

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 precise verb and resource — merge the base into the head of a PR branch server-side — and anchors it to a known UI action ('Update branch'). The explicit 'Never a force-push' clause separates it from any branch-rewriting sibling, and the merge-commit semantics distinguish it from merge_pr and resolve_pr_conflict.

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?

Gives a clear condition for use (branch is behind its base) and clarifies the mechanism is a server-side merge through the push gates rather than a rebase or force-push. It also tells the agent what to do on failure via conflictFiles, though it does not name the sibling tools to escalate to for conflict resolution.

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