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

Annotations already indicate read-only, idempotent, and non-destructive behavior. The description adds meaningful behavioral context beyond those annotations: it states that pull requests are filtered out automatically and that the default state is 'open'. These are useful details not present in the annotations, so the description adds value without contradicting them.

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 two concise sentences with front-loaded information. It states the purpose first, then adds the PR filter and return fields, and finally the default. Every word earns its place, with no redundancy or fluff.

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?

The tool has a simple operation with clear scope, defaults, and return fields listed. The schema handles parameter boundaries, and the description covers the behavioral nuance (PR filtering). Some might argue that pagination or sorting isn't mentioned, but per_page is already in the schema and the default open state is stated. This is complete enough for the tool's complexity.

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?

The input schema covers 100% of parameters, including descriptions for state and per_page. The description reinforces owner/repo naming and the default state, but it doesn't add any new semantics or clarify parameter formats beyond what the schema already provides. Therefore, a baseline of 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?

The description clearly states a specific verb ('List'), the resource ('issues for a GitHub repository'), and the key scoping parameters (owner and repo name). It also distinguishes itself from related tools by explicitly noting that pull requests are filtered out automatically, which is a unique behavioral detail beyond a generic 'list issues'.

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 implies when to use the tool: when you need issues for a specific repo, with a default to open issues. It mentions the repository scoping (owner/repo) and the automatic PR filtering, which guide usage. However, no explicit alternatives are named, and there is no 'when not to use' guidance, so it falls short of a 4.

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