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

Annotations already declare destructiveHint=true and openWorldHint=true, so the safety profile is covered. The description adds genuinely non-annotated behavior: partial-update semantics ('Only the fields you pass change'), the state machine linking scheduledAt/useNextSlot/publishNow to scheduling and retrying a failed post, and the immutability of published posts.

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?

Four short sentences, front-loaded with applicability ('Edit a draft, scheduled or failed post') before the parameter behavior. No filler, no restatement of the title, and each sentence carries a distinct constraint.

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 an 18-parameter tool with nested per-platform objects and no output schema, the description covers the update model, the scheduling side effects and the one hard restriction, which is the right level of detail. Return values need not be explained; the only omission is that it doesn't warn that accountIds overwrites existing targets.

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 interaction semantics the schema cannot express — that scheduledAt, useNextSlot and publishNow all schedule (and retry a failed post) and that draft:true reverts a post to drafts. It still doesn't flag that accountIds replaces existing targets, which is the riskiest param behavior.

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?

Opens with a specific verb+resource and immediately scopes it: 'Edit a draft, scheduled or failed post' followed by the editable facets (text, media, target accounts, time, platform options). An agent can distinguish it from create_post, delete_post and list_posts 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?

Gives a clear when (draft/scheduled/failed posts) and an explicit when-not ('Published posts can't be edited'), plus the trigger conditions that reschedule or retry a post. It does not name an alternative tool (e.g. create_post) for the published-post case, so it falls just short of a full routing statement.

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