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

Annotations already declare readOnlyHint and destructiveHint as safe, so the description does not need to repeat that. It adds the organisational scope ('available to your organisation'), which is useful but minimal. No deeper behavioral detail (e.g., authentication requirements, installation state filtering) is disclosed, but given the annotations cover the safety profile, a 3 is appropriate.

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, no fluff. The first sentence states the core purpose; the second describes output consumption. All information is front-loaded and every word 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?

An output schema exists, so return-value documentation is not needed. The description covers the essential usage: listing installations and linking to dependent tools. It does not mention potential prerequisites (e.g., prior setup via start_github_install) but that is a minor gap for a simple list operation with no parameters.

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?

There are zero parameters, so the 0-parameter baseline of 4 applies. The description adds nothing about parameters because there are none, and the schema obviously has 100% coverage. This is a trivial but correct score.

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 clearly states the action ('List') and the target resource ('GitHub App installations'), scoped to 'your organisation'. It also directly names the sibling tools that consume the returned installationId, which differentiates it from other list tools like list_projects or list_glossary.

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 explicitly tells the agent what to do with the output (use the installationId with list_repository_branches, detect_repository, and connect_repository), giving actionable guidance. It does not explicitly mention when not to use it or a direct alternative, but the connection to these siblings makes the usage context reasonably clear.

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