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

Annotations already declare readOnlyHint=true, and the description adds valuable behavioral context: 'Losing paid access only removes paid capabilities; no lifecycle, claim or receipt history is ever deleted.' This clarifies data persistence and mutation effects beyond what annotations provide. The description also details what the read returns, enhancing transparency.

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 front-loaded with the core purpose and data, followed by parameter requirements and a behavioral note. At three sentences, it is concise and avoids redundancy. Minor improvement could be possible by tightening the parameter sentence, but overall it is well-structured.

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 read-only tool without an output schema, the description adequately lists the returned fields and adds behavioral context. It is missing explanations of terms like 'principal' or 'Factory', and does not hint at error conditions or response structure, but given the tool's simplicity, the coverage is sufficient for most use cases.

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?

With 0% schema description coverage, the description should compensate by explaining the parameters. It merely states 'Requires the principal_id and its principal_key' without adding meaning beyond their names. No format, examples, or purpose are given, leaving the agent underinformed about what values to provide.

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 uses a specific verb 'Read' and clearly identifies the resource as 'one principal's account-level Factory membership'. It lists the exact data returned (subscription status, plan, period end, plan capabilities, slot usage), which distinguishes it from sibling tools like factory_status or factory_health that serve different purposes.

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 states the required parameters (principal_id and principal_key) but does not explicitly tell when to use this tool versus alternatives. It implies usage for reading membership details, but no when-not-to-use or alternative tool suggestions are provided, leaving the agent to infer context from the tool's name and purpose.

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