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

No annotations are provided, so the description carries the full burden — and it does: it discloses cost (free via x402 vs. the paid delta), the exact return shape with no rows, the HTTP GET endpoint, polling cadence, and the cursor-based increment pattern. This is well beyond what a bare schema would convey.

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?

Front-loaded and mostly efficient, but the 'Free:' prefix duplicates the later 'price free via x402', and the bracketed HTTP/docs footer is somewhat extraneous. Still, every clause carries operational meaning.

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 one-param, no-output-schema tool with no annotations, the description covers cost, return fields, polling strategy, and the relation to the paid delta. An agent has everything needed to invoke and route it correctly.

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% (the single 'since' param is fully documented as an opaque cursor with bootstrap semantics), so the schema already does the work. The description restates 'since your cursor' but adds no syntax or format detail beyond it. Baseline 3 applies.

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?

States a specific verb+resource (count of calendar events added or resolved changed since cursor) and explicitly scopes it as a polling probe over /v1/calendar/delta, returning only changed_count/next_cursor/as_of. It clearly distinguishes itself from the sibling probability_calendar_delta by saying it returns 'no rows'.

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?

Gives explicit when-to-use guidance: 'Poll hourly for $0 and call the paid delta only when changed_count > 0.' It names the alternative (the paid delta) and the exact condition that selects it, leaving nothing to inference.

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