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

Annotations give the safety profile (readOnlyHint=false, destructiveHint=false, idempotentHint=true), and the description adds non-redundant behavior: the post persists in the calendar as cancelled, the response is the post's current state, and cancellation fails once publishing has begun. The non-destructive framing in the text is consistent with destructiveHint=false rather than contradicting it.

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?

Three compact sentences ordered effect-first, then lifecycle alternatives, then precondition. Every clause carries information an agent needs; nothing is repeated from the title or schema.

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 single-parameter state-change tool with no output schema, the description covers effect, return value, persistence semantics, recovery paths, and the failure precondition. There is no gap an agent would need to guess at before calling it.

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 description coverage is 100%, and the single postId parameter already documents its pattern and provenance (postfjord_list_calendar or postfjord_create_draft). The description adds no parameter-level detail, so the schema carries the load and the 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?

The description states a specific verb and resource ('Cancels a scheduled post so it will not be published') and immediately distinguishes the outcome from its siblings. It names both postfjord_schedule_post (re-times) and postfjord_delete_post (removes), so an agent can separate cancellation from rescheduling and deletion without opening a schema.

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?

Explicit routing: use this to cancel and keep the entry, use postfjord_schedule_post to give it a time again, use postfjord_delete_post to remove it. It also states a when-not condition ('already publishing or published cannot be cancelled'), covering both the alternatives and the exclusion.

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