testflight__assign_build_to_groups

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

Goes beyond the annotations by disclosing that it checks existing assignments, reports per-group results including partial failures, and that external groups may require beta app review before testers can install. That is meaningful operational context (fan-out failure semantics, downstream gating) not present in readOnlyHint/destructiveHint. "RELEASE-level write" is a vague label, and it does not say whether existing assignments are preserved or replaced.

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?

Four short sentences, front-loaded with the core action, then behavior, then the review caveat, then severity. No padding, though the trailing "RELEASE-level write" tag is low-information jargon rather than content.

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?

With no output schema, the description usefully explains the reporting shape (per-group results, partial failures) and the eligibility prerequisites. Gaps remain on permission requirements and idempotency for what annotations mark as a destructive write, but the description is largely sufficient for correct invocation.

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% (app, build, groups all documented with format guidance and the "ambiguous matches are refused" rule), so the schema carries the parameter burden. The description only adds the "processed, unexpired" constraint on the build, which is marginal. 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?

Specific verb and resource with scope qualifiers: "Assign one processed, unexpired TestFlight build to named beta groups." An agent immediately knows the action and the eligibility constraint on the build. It does not, however, distinguish itself from overlapping siblings such as builds__beta_groups__add or beta_groups__builds__add, so it stops short of a 5.

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?

Usage is implied through preconditions ("processed, unexpired" build, "named beta groups") and the external-group caveat, but it never states when to pick this tool over the near-identical sibling add-build-to-group tools. No explicit alternatives or exclusions are given.

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