add_github_project_sub_issue

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

Beyond the annotations (write, idempotent, non-destructive, open-world), it discloses required scopes (project.write, item.relationship.write, global write gate), the no-parent-replacement rule, that both directions are re-read and an audit record is persisted even on no_change, and an explicit no-auto-retry directive. This is unusually rich behavioral context for an agent.

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 core action is front-loaded and every sentence carries information. The telegraphic fragments ('Single relationship only.') read as an unformatted list, which slightly hurts scanability but wastes nothing.

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 write tool with no output schema, the description covers permissions, scope constraints, audit behavior, idempotency nuance, and failure handling. An agent has enough to call it correctly and safely without opening the schema.

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 0%, so the description must carry the burden. It does clarify the source-vs-target roles (source is the parent, target becomes the child), which is the key semantic distinction, but owner and number are left entirely undefined.

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 first sentence names the exact verb and resource: 'Add target as a sub-issue of source.' This clearly distinguishes it from remove_github_project_sub_issue, add_github_project_blocked_by, and add_github_project_item, all of which operate on different relationship types.

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?

It gives real usage constraints (never replace an existing parent, single relationship only, both items must share an authorized Project, no automatic retries). It stops short of explicitly naming when a sibling such as add_github_project_blocked_by or remove_github_project_sub_issue should be used instead, leaving that to inference.

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