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

No annotations, so the description carries full burden. It discloses cursor stability ('Cursors are stable across restarts'), pricing ('price $0.005 via x402'), and the pay-only-when-needed strategy. It doesn't describe response payload structure beyond 'changed_count and a new next_cursor', but that's substantial behavioral context for a stateless read.

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 dense and front-loaded with the core purpose, but has notable redundancy: 'added or resolved changed since your cursor' and 'added or resolved added or changed' repeat the same phrasing awkwardly. The HTTP/pricing/docs footer is necessary metadata but adds length. It's serviceable but could be tightened.

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 1-param delta endpoint with no output schema and no annotations, the description covers the essential mechanics: cursor usage, bootstrap behavior, stability, pricing, and the cheaper alternative. It doesn't explain the full response shape (what fields each event contains), but that's arguably beyond scope for a delta cursor 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?

Only 1 parameter, schema description coverage is 100%. The schema already documents the 'since' cursor semantics ('Opaque cursor from a previous next_cursor; omit once to bootstrap'). The description adds the usage pattern (pass since from last call) but no syntax or format beyond the schema. Baseline 3 is appropriate.

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 opening sentence states a specific verb+resource+scope: 'Only the calendar events added or resolved changed since your cursor (delta of /v1/calendar)'. This clearly identifies the tool as a delta/changes endpoint for calendar events. Siblings like probability_calendar and probability_calendar_changes exist, but the description doesn't explicitly contrast against them.

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?

Explicitly tells the agent when to use: 'pass since=<next_cursor from your last call>' and 'Omit since once to bootstrap'. Names an alternative: 'Poll the free sibling /v1/calendar/changes for counts and pay only when there is something to fetch.' This is textbook when/when-not/alternative guidance.

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