Compute exact age in years, months and days from a birth date, with the next birthday. Pure CPU, instant.
Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.
{
"id": 1,
"jsonrpc": "2.0",
"method": "tools/call",
"params": {
"arguments": {
"dob": "<dob>"
},
"name": "age"
}
}| Name | Required | Description | Default |
|---|---|---|---|
| dob | Yes | Date of birth |
Changes observed during successful MCP inspections.
Input schema / properties / dobAdded value: +{
+ "description": "Date of birth",
+ "type": "string"
+}Input schema / requiredAdded value: +[
+ "dob"
+]Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are supplied, so the description carries the burden. 'Pure CPU, instant' usefully signals a local, deterministic, side-effect-free calculation with no auth or rate limits, which is meaningful context. However, it doesn't state what happens with a malformed or future date, nor explicitly confirm there are no side effects, so the disclosure is partial.
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?
Two short sentences, front-loaded with the core computation and followed by the output detail and a performance note. Nothing is padded or repeated.
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 trivial single-parameter calculation with no output schema, the description covers what it returns (years/months/days plus next birthday) and its cost profile. The only real gap is the accepted date input format, which would prevent a failed call.
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?
There is a single parameter with 100% schema coverage, so the schema already documents dob. The description restates it as 'birth date' but adds no format detail (ISO 8601? locale-dependent?), which is the one piece of meaning the schema doesn't supply. Baseline 3 is appropriate.
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 names a specific verb and resource ('Compute exact age') and enumerates the output shape (years, months, days, next birthday), which is far more than a restatement of the name. It stops short of differentiating itself from near neighbours like date_calc, business_days, or week_number, so it doesn't reach 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?
Usage is implied by the purpose — you call it when you have a birth date and want an age — but there is no explicit when-to-use versus date_calc, and no guidance on invalid or partial dates. Adequate but leaves the agent to infer the boundary against sibling date tools.
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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