PubNub MCP Server

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

With no annotations provided, the description carries the full burden and effectively discloses key behavioral traits: signals are lightweight, fast, not stored in message history, and have a 30-character payload limit. It does not mention rate limits, authentication needs, or error handling, leaving some gaps.

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 front-loaded with the core purpose in the first sentence, followed by clarifying details and usage guidance in the second, with no wasted words. Both sentences earn their place by adding essential context and instructions.

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 moderate complexity (2 parameters, no output schema, no annotations), the description is largely complete, covering purpose, behavior, and usage. However, it lacks details on response format or potential errors, which could be helpful for an agent invoking 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 description coverage is 100%, so the schema already documents both parameters ('channel' and 'message') with their types and constraints. The description adds minimal value by reiterating the 30-character limit for 'message', but does not provide additional semantics beyond what the schema offers.

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 specific action ('Sends a PubNub Signal'), identifies the resource ('to a specified channel'), and distinguishes it from siblings by specifying lightweight, non-stored messages with a 30-character limit, unlike other tools like 'publish_pubnub_message' which likely stores messages.

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 explicitly states when to use this tool ('Call this tool when you need to send small, real-time notifications or presence indicators'), providing clear context for its application, and implicitly distinguishes it from alternatives like 'publish_pubnub_message' by noting signals do not get stored in history.

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