Pub/sub: publish a message to a topic. Send { topic, token, data }. [x402 paid tool — price $0.003; POST /api/pubsub/publish]
| Name | Required | Description | Default |
|---|---|---|---|
| data | Yes | Message payload | |
| token | Yes | Your secret token | |
| topic | Yes | Topic name |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Discloses paid nature with cost ($0.003) and HTTP endpoint. No annotations, so description provides some behavioral context but lacks details on idempotency, failure modes, or side effects.
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?
Brief and front-loaded with key info (action, required data). Includes useful metadata in brackets; no wasted words.
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?
Minimal tool with three simple parameters and no output schema. Description covers purpose and cost, but lacks return type or error handling info; adequate for a simple publish action.
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% with descriptions for each parameter. Description adds no extra meaning beyond listing names; baseline 3 applies.
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?
Clearly states 'publish a message to a topic' with required parameters listed. Distinguishes from sibling pubsub_poll implicitly by verb, but no explicit differentiation.
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 on when to use this vs alternatives like pubsub_poll. No context about prerequisites or typical use cases.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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