Will this branch name pass the repo's hooks?

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

Annotations already state readOnly and idempotent. The description adds that it uses 'configured type allow-list' and honors 'extra_branch_types from config', which tells the agent that behavior depends on repo config, not a fixed regex. This goes beyond the annotations by clarifying the underlying 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?

Two sentences, the first directly states the action, the second adds rationale. No redundancy, front-loaded with the primary purpose. Each sentence earns its place.

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 one-parameter read-only tool, the description covers purpose and usage. An output schema exists to document return values, so it's not needed here. It might mention edge cases, but given the simplicity, it's complete enough.

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?

The schema has a single parameter branch_name with no description (0% coverage). The description clarifies that the parameter is the branch name to validate against the repo's allow-list, which gives it meaning. However, it doesn't specify any format or constraints beyond that, so it only partially compensates for the missing schema description.

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 'Check a branch name against this repo's configured type allow-list before you create it', which is a specific verb (check), resource (branch name), and context (allow-list). It clearly distinguishes from siblings like rrt_validate_commit (commits vs branches) and rrt_branch_new (creating a branch). The title reinforces the purpose.

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 says 'before you create it' and explains it's 'Cheaper than creating it and having the pre-commit hook reject it', which tells the agent to use this as a pre-flight check. It also notes it honors config, implying it's more accurate than hardcoded checks, but doesn't explicitly name alternatives; however, it's clear enough.

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