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

The description discloses an important side effect not visible in the schema or annotations: the inverse link is written automatically, so 'blocks' also records 'blocked by.' This goes beyond the annotations' readOnly/destructive/idempotent hints and gives the agent meaningful behavioral context.

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, efficient sentences front-load the primary action and then provide the most important behavioral detail. There is no redundant or filler content, and every sentence 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?

For a simple mutation with three required parameters, a fully documented schema, and safety annotations, the description is largely complete: it states the operation, directionality, and automatic inverse behavior. A note on how to remove relations or handle duplicate relation types could improve it, but nothing essential for a correct call is missing.

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 100% and all three parameters, including the type enum, are already documented. The description adds value by explaining how relation types behave symmetrically, but it does not add further parameter-level semantics beyond what the schema provides.

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 operation: 'Link two issues.' It also adds useful semantic detail about automatic inverse links, which clarifies the tool's behavior. However, it does not explicitly differentiate from sibling tools like mark_issue_duplicate or remove_relation, so it is clear but not maximally discriminative.

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?

No guidance is provided about when to use this tool versus alternatives. An agent must infer when set_relation is appropriate instead of mark_issue_duplicate or remove_relation; there is no when/when-not context or mention of alternatives.

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