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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the bar for adding value is lower. The description confirms these behaviors ('Every call is read-only and idempotent') and adds important context about error handling: it never raises a protocol error but returns a JSON error object with fix instructions. This goes beyond the annotations.

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 concise and well-structured: it starts with the primary purpose, provides a clear example, gives usage guidance, and ends with error handling. Every sentence adds value, and there is no redundancy or fluff.

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 the tool has an output schema (not shown but indicated), the description does not need to fully detail return values, but it still provides a typical output example. It covers all key aspects: purpose, input, output, error handling, and safety. With 3 well-documented parameters and rich annotations, the description is complete and leaves no gaps for an agent.

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 coverage is 100% with detailed descriptions, so the baseline is 3. The description adds value by providing a typical input example that clarifies parameter relationships, notes the default for monthly_revenue, and describes the output structure. This aids understanding beyond what the schema alone provides.

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 computes months of cash runway and projected out-of-cash date. It provides a concrete example of input and output, making the purpose specific and unambiguous. Additionally, it distinguishes itself from the sibling tool 'unit_economics' by stating what it is not for.

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 explicitly tells when to use the tool ('when a cash balance and a monthly burn are known') and when not to use it ('Not for per-unit profitability (unit_economics)'). It also explains error handling behavior and that it is safe to retry after correcting input, providing clear guidance on usage.

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