add_labels

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

With no annotations, the description carries the transparency burden. It discloses the key additive behavior ('keeping the issue's existing labels'), but does not mention error handling, authentication requirements, or what happens with duplicate or invalid label names. The docs link offers external reference but is not inline behavioral disclosure.

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 followed by a documentation link. Every word earns its place, and there is no redundant fluff or repetition of schema information.

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 mutation tool with four required parameters and 100% schema coverage, the description covers the purpose, the key behavioral nuance, and points to official docs. It could mention prerequisites (e.g., issue must exist) or return behavior, but that is implied by the GitHub API context. Overall, it is sufficient for an agent to select and invoke correctly.

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 the baseline is 3. The description does not add further parameter-level meaning beyond the schema, but it does not need to—the schema already documents all four parameters adequately.

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+resource construction: 'Add labels to a GitHub issue', and adds a critical qualifier 'keeping the issue's existing labels'. This clearly distinguishes it from sibling tools like remove_label or update_issue, and precisely communicates the tool's function.

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 phrase 'keeping the issue's existing labels' gives clear context that this tool is for adding labels without overwriting current ones, implying when to choose it over a replace-style operation. However, it does not explicitly name alternative tools or state when not to use it.

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