ChartMogul MCP Server

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are provided, so the description carries the full burden. It discloses that this is a creation operation ('Create subscription event') and mentions the return value ('Returns created subscription event object'), but lacks details on permissions, error handling, rate limits, or whether it's idempotent. It adds some behavioral context but not comprehensively.

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 well-structured and front-loaded with the purpose, followed by parameter details and return value. It's concise with no wasted sentences, though it could be slightly more streamlined by integrating the field list more clearly.

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 no annotations, 0% schema coverage, no output schema, and 1 nested parameter, the description does a fair job by specifying fields and return type. However, it lacks details on authentication, error cases, and the 'list above' reference for event_type is unclear, leaving gaps for a creation tool.

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?

The input schema has 0% description coverage with 1 parameter ('data' as an object). The description lists specific fields (e.g., external_id, customer_external_id) that should be included in 'data', adding significant meaning beyond the schema. However, it doesn't fully explain how these fields map to the 'data' object structure or provide examples, leaving some ambiguity.

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: 'Create subscription event for Custom API data sources' and specifies it's 'Used to track subscription lifecycle changes.' It distinguishes from siblings like 'list_subscription_events' (read) and 'update_subscription_event' (modify) by focusing on creation.

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 implies usage context ('for Custom API data sources') and distinguishes from siblings by its creation focus, but does not explicitly state when to use alternatives or any prerequisites. It mentions 'event_type (string: from list above)' which hints at a predefined list, but doesn't specify where to find it.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.