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

Annotations already declare readOnlyHint=true, openWorldHint=true and destructiveHint=false, so the safety profile is covered. The description still adds genuine context the annotations do not: the result ordering and the important gotcha that PRs are filtered out of issue listings. It stops short of describing pagination or return shape, which keeps it below a 5.

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 short sentences with zero filler. The primary behavior and its sorting are front-loaded, and the sibling routing is placed in a compact trailing clause.

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 read-only list tool with 100% schema coverage and annotations covering safety, the description supplies everything needed to select and invoke it, including the PR exclusion that would otherwise cause surprise. Only return-field expectations and pagination behavior are unaddressed, which is minor given there is no output 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 coverage is 100%, so repo format, limit bounds (default 20, max 100), state enum with its default, and comma-separated labels are all fully documented in the schema. The description only echoes that state/label filtering exists, adding no format or syntax detail beyond structured fields. Baseline 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?

Specific verb (List) plus resource (issues) plus scope (in a GitHub repository) plus ordering (most recently updated first). It explicitly excludes pull requests and names the sibling to use instead, so an agent can separate it from github_list_prs and github_get_issue 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?

States the filtering conditions it supports (state, label) and explicitly names the alternative for the case it does not cover: "Pull requests are left out; use github_list_prs for those." Nothing about when to pick this tool over its sibling is left to inference.

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