register_subscription

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

With no annotations, the description covers key behaviors: non-historical event capture, no TTL, and return type. It omits potential side effects but is otherwise transparent for a creation tool.

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?

Three efficient sentences. The first immediately states the core purpose, the second adds behavioral nuance, and the third covers TTL. No redundant information.

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?

Despite no output schema, it specifies the return type (FGuid string) and explains cursor behavior, TTL, and relationship with siblings. This is sufficient for an agent to use the tool correctly.

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 provides 100% coverage with a clear description of event_filter (substring-match, OR-combined). The description does not add further detail, meeting the baseline for high schema coverage.

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 tool creates a server-side cursor and filter on the event bus, returning a subscription_id. It distinguishes itself from siblings like poll_subscription and unsubscribe by naming them explicitly.

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?

It explains that the cursor starts at the current next_seq, so only future events are captured, and that subscriptions have no TTL (need manual unsubscribe). This provides clear context for when to use and how to manage lifecycle, though it doesn't explicitly list when not to use.

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