iss_nowCurrent latitude / longitude of the International Space Station.
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
| Name | Required | Description | Default |
|---|---|---|---|
| message | Yes | Response status message | |
| timestamp | Yes | Unix timestamp of the observation | |
| iss_position | Yes |
Changes observed during successful MCP inspections.
Input schema / examplesAdded value: +[
+ {}
+]Output schema / (root)Previous value: -nullNew value: +{
+ "properties": {
+ "iss_position": {
+ "properties": {
+ "latitude": {
+ "description": "ISS latitude coordinate",
+ "type": "string"
+ },
+ "longitude": {
+ "description": "ISS longitude coordinate",
+ "type": "string"
+ }
+ },
+ "required": [
+ "latitude",
+ "longitude"
+ ],
+ "type": "object"
+ },
+ "message": {
+ "description": "Response status message",
+ "type": "string"
+ },
+ "timestamp": {
+ "description": "Unix timestamp of the observation",
+ "type": "number"
+ }
+ },
+ "required": [
+ "timestamp",
+ "iss_position",
+ "message"
+ ],
+ "type": "object"
+}Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false. The description adds a key behavioral aspect: it returns latitude/longitude, which informs the agent of the data format. No contradictions.
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?
A single, clear sentence with no extraneous words. Perfectly concise for the tool's simplicity.
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 zero parameters, read-only annotations, and an output schema (presumably containing lat/lng), the description is complete. It tells the agent exactly what the tool does and returns.
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?
No parameters, so schema coverage is 100% (empty object). The baseline for 0 parameters is 4. Description adds no parameter info because none needed.
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 explicitly states the tool returns the current latitude and longitude of the ISS, providing a specific verb (returns) and resource (ISS location). It distinguishes itself from siblings, which are mostly search, research, or subscription tools.
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?
Clear context: use when you need the current ISS coordinates. No explicit when-not or alternatives, but due to its unique nature, the usage is self-evident. Minor deduction for lack of explicit guidance.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.