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

Annotations already indicate this is a mutating operation (readOnlyHint=false) and not marked destructive. The description adds valuable behavioral context beyond annotations: partial updates, null semantics for clearing assignee/project/cycle, and empty reviewers array clearing. This meaningfully clarifies side effects.

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, tightly packed with the most important usage semantics, with zero filler. The core operation is stated first, and the clearing behavior follows as a concise caveat.

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 tool with 14 parameters and no output schema, the description provides the essential cross-cutting behavior needed to call it correctly. It does not describe return values, but for an update operation this is not a blocker. The absence of an explicit 'use create_issue for new issues' exclusion is minor.

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 high (79%), so the schema explains most parameters. The description adds important cross-parameter semantics: only provided fields are updated, and null/empty values have a clearing effect rather than being ignored. This is exactly the kind of behavior that an agent cannot reliably infer from individual parameter descriptions alone.

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?

States a specific verb ('Change') and resource ('an existing issue'), which clearly distinguishes it from create_issue, delete_issue, and move_issue. The scope is unambiguous and the meaning is obvious.

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 communicates this is for modifying an existing issue, not creating one, and adds critical partial-update semantics: only passed fields are touched. It does not explicitly name alternatives like create_issue, but the usage context is clear enough for an agent to select it correctly.

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