Retire mass_g of verified credits for a buyer: cheapest-first matching, exactly-once (idempotent on purchase_id), returns a content-addressed offset certificate with per-fill costs. Payment settles via escrow. dry_run=true previews the exact fills/cost without mutating the book.
| Name | Required | Description | Default |
|---|---|---|---|
| buyer | Yes | ||
| mass_g | Yes | ||
| dry_run | No | ||
| purchase_id | Yes |
| Name | Required | Description | Default |
|---|---|---|---|
| result | Yes |
Changes observed during successful MCP inspections.
Input schema / properties / dry_runAdded value: +{
+ "default": false,
+ "title": "Dry Run",
+ "type": "boolean"
+}Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The description says the operation is 'exactly-once (idempotent on purchase_id)', but the annotations declare idempotentHint=false. That is a direct contradiction on a key behavioral property, which is especially important for a mutating purchase/retirement tool. Payment escrow and dry_run context are useful, but the contradiction mandates a low score.
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 compact and front-loaded, starting with the core action and then explaining matching, idempotency, output, settlement, and dry_run. Every sentence adds useful information without repetition.
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 complex mutating tool with an output schema, the description covers the operation, matching behavior, idempotency intent, certificate return, escrow settlement, and dry_run semantics. The main incompleteness is that the idempotency statement conflicts with annotations rather than clarifying them.
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 0%, so the description must carry parameter meaning. It explains mass_g as the amount retired, purchase_id as the idempotency key, and dry_run as a non-mutating preview. Buyer is only minimally described as 'for a buyer', but the other three parameters are clarified well.
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 states a specific verb and resource: 'Retire mass_g of verified credits for a buyer.' It also explains matching, certificate output, and escrow settlement, so the agent can understand the operation without opening the schema. It does not explicitly distinguish itself from the sibling buy_offset_budget tool, keeping it just below 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 gives clear context for using dry_run=true to preview without mutating the book. However, it never states when to choose buy_offset over buy_offset_budget or when not to use this tool, so usage guidance is mostly implied rather than explicit.
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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