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

Annotations already cover the safety profile (readOnly=false, destructive=false, openWorld=false), and the description adds real behavior: creates are rejected without both latitude and longitude, custom slugs are only valid on Activity objects and not on lodging/transportation/expense/trip resources, and it is scoped to the authenticated user's account. It doesn't describe return behavior, but an output schema exists and covers that.

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 core guidance is front-loaded, but the text is heavily redundant: the instruction that MCP clients must convert UTC starts_at/ends_at to the activity timezone appears three times, and the 'custom slugs are only valid on Activity objects' rule is restated in three separate places. Roughly a third of the description repeats prior sentences instead of earning its place.

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 16-parameter create tool with a nested 'data' bag and an output schema, the description covers the hard parts: mandatory coordinates, timezone conventions, category slug policy, and reservation codes. Field-level detail like price/currency pairing and the merge-precedence of the raw 'data' object is left to the schema descriptions, which is acceptable.

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%, so the baseline is 3, but the description adds meaningful semantics: it supplies the built-in activity_type slug vocabulary (the schema declares no enum), the rule to store provider-issued codes in provider_reservation_code, and the UTC-to-timezone contract for starts_at/ends_at. That is genuine value beyond the schema, though much of the slug/custom-category text is repeated rather than refined.

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 and resource ('Create a Tripsy activity'), and the follow-up definition of what counts as an activity (stop, reservation, meal, tour, event, experience) helps separate it from sibling creators like tripsy_hostings_create or tripsy_expenses_create. It never names those alternatives explicitly, so sibling disambiguation is implicit rather than stated.

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 concrete usage rules: one activity per actual stop, latitude/longitude are mandatory, 'include address when known', UTC timestamps with a local IANA timezone, and no ad hoc activity_type values such as 'sightseeing'. It stops short of stating when to use this tool instead of a hosting/transportation/expense record, which is the main gap.

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