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

The description discloses cost ($0.02 per subscription), which actions are free, and the API key requirement. This goes beyond the annotations which only indicate non-read-only and non-idempotent. It clarifies that subscribe/unsubscribe mutate state while matches/list are reads, providing useful behavioral context without contradicting annotations.

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 only three sentences, with the purpose front-loaded. The action list is compact and includes costs, making every sentence informative. No filler or redundant content.

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?

Given the tool's complexity (multiple actions, 4 parameters) and no output schema, the description covers all actions, costs, auth requirements, and a use case. It does not explain return values or parameter-to-action mapping, but those are already in the schema, so the description is reasonably complete for an agent to decide when and how to invoke the tool.

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 baseline is 3. The description adds semantic value by explaining the 'action' parameter with costs and providing example values for 'keyword' and 'namespace'. This enhances the schema descriptions rather than merely repeating them, justifying a 4.

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's function: 'Subscribe to keyword/namespace alerts in The Hive.' It specifies the resource (The Hive), the event-driven behavior (new matching entries appear in matches feed), and differentiates it from sibling tools like x711_hive_read and x711_hive_write. The action list further clarifies the tool's scope.

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 provides a concrete use case ('competitive intelligence') and examples like watching '/defi/base'. It also enumerates the four actions with their costs, implying when to use each. However, it does not explicitly compare with alternative tools or state when not to use this tool, so it stops short of a 5.

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