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

No annotations are provided, so the description carries full responsibility for behavioral disclosure. It explicitly states that attaching does not replay earlier changes, that delivery starts now, and that older history is available through subject_history. This covers key side effects and limits, though it does not detail permissions or reversibility, which are less critical for a read-like attachment operation.

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 sentences with zero fluff. The primary purpose is stated first, followed by a crucial behavioral caveat (no replay) and a pointer to an alternative for history. Every sentence earns its place and the structure is front-loaded.

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 one parameter, no output schema, and no annotations, the description is complete. It explains the core effect, the non-replay behavior, and where to get older history, giving an agent everything needed to call it correctly without further research.

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 schema already describes the only parameter (setId) with 'From list_sets.' at 100% coverage. The description adds no additional meaning beyond what the schema provides, so the baseline of 3 is appropriate. The description does not elaborate on format or validation, but the schema is sufficient.

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 uses a specific verb 'attach' with a clear resource 'subscription set' and explains the outcome ('changes reach you'). It also differentiates from siblings by specifying how what_changed_since behavior changes and contrasts with subject_history for older data, making its purpose unambiguous.

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 clearly explains the effect of attaching and distinguishes it from replaying history, implying when to use it (when you want live changes from an existing set) versus accessing historical data via subject_history. It does not explicitly name alternatives like subscribe, but the behavioral contrast provides sufficient context for selection.

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