Get combined commit status

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

Beyond the readOnlyHint/openWorldHint annotations, it discloses two non-obvious behaviors: state is omitted entirely when the instance reports nothing for the ref (a real edge case), and target_url is returned relative to the instance origin so the host must be prefixed before following. Neither fact is derivable from annotations or schema.

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?

Front-loaded with the purpose and the routing decision in the first two sentences, with the edge-case and URL caveats after. Dense but every sentence carries information; the only mild cost is a packed third sentence combining two distinct caveats.

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 does real work by naming the possible state values, noting the per-check latest-state detail, and covering the omitted-state and relative-URL cases. It stops short of describing the remainder of the response envelope (e.g. the checks collection and its fields), which is the main residual gap.

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 baseline is 3; the description adds a little by framing ref as 'the commit, branch or tag to judge' and showing the composite (owner/repo/ref) addressing form. Most semantic weight still sits in the schema, so it is only a modest lift above baseline.

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 specific verb and resource ('rolled-up CI verdict for a commit, branch or tag') and enumerates the exact output states (success, pending, failure, error, warning). It explicitly distinguishes itself from the sibling get_commit_statuses, so an agent can choose without opening either schema.

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 an explicit decision rule: 'This is the tool for "did CI pass?"', then says the sibling returns transition history which is 'the wrong shape for that question.' Both the when and the when-not are stated with a named alternative.

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