Look up the referral link we hold for a vendor, with the reader benefit and every restriction attached to it. We hold codes for a handful of vendors and earn a commission on them; /disclosure lists all of them.
| Name | Required | Description | Default |
|---|---|---|---|
| vendor | Yes | Vendor name to get the referral code for (e.g. 'Railway') |
Changes observed during successful MCP inspections.
Input schema / properties / api_keyRemoved value: -{
- "description": "Your API key from register_agent, for attribution tracking. Optional — unauthenticated calls still return the code.",
- "type": "string"
-}Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true and destructiveHint=false, indicating a safe read-only operation. The description adds that the tool holds codes for a limited set of vendors and earns commission, but doesn't disclose specifics like rate limits, pagination, or whether the code is returned as a link or a string. Given the annotations cover safety, a 3 is appropriate.
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 no wasted words. It front-loads the primary purpose and then provides important context about the limited vendor list and the disclosure alternative. Perfectly concise.
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 simple single-parameter read-only tool, the description is quite complete. It covers what the tool does, the constraint on vendors, and points to an alternative for a full list. The only minor gap is the lack of explicit return format, but given the simplicity and no output schema, this is not critical.
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 the 'vendor' parameter is well-described in the schema. The description adds that the vendor must be among those for which codes are held, but doesn't go beyond the schema's example. Since the schema does he heavy lifting, a baseline of 3 is correct.
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 purpose: to look up the referral link held for a specific vendor. It specifies the resource (referral link) and the action (look up), and mentions the context of commissions and disclosure, which helps differentiate it from sibling tools like search_deals or compare_vendors. However, it doesn't explicitly compare itself to siblings, so it's slightly less than a 5.
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 clear context on when to use the tool: to retrieve a referral code for a vendor. It also implies that there is a curated list of vendors (only a handful) and points to /disclosure for a full list, which gives the agent an exclusion criterion. It does not explicitly say 'use this instead of X' but the context is sufficient.
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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