Preflight publish

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

The annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, and the description is fully consistent with that while adding real value: it discloses the media-rule validation, the 24 h quota check, and the return payload (approval_id plus the exact planned Graph calls). It does not say what a failed validation returns or how long an approval_id remains valid, which keeps it below the top mark.

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 front-loaded sentences with no filler: scope, then the validation/scheduling behavior, then the safety gate and return value. Nothing is repeated from the annotations or schema verbatim.

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, nested-object tool with no output schema, the description covers the happy path and the approval gate but leaves the agent without guidance on constraint violations, per-kind media requirements, or what a rejected preflight looks like. Adequate to invoke correctly in the common case, incomplete for the complex one.

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 only 25% across 16 parameters, so the description must carry the load, yet it only touches media sourcing (url vs path), kind selection, and publish_at. The many undocumented options — cover, alt_text, user_tags, trial_reel, collaborators, share_to_feed, is_ai_generated, thumb_offset_ms, is_paid_partnership, branded_content_sponsor_ids — get no mention, and no cardinarity rules (e.g., carousel item counts) are given.

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 gives a precise verb pair ("Validate and preview publishing") plus the enumerated resource kinds (image, reel, story, carousel) and the accepted media sources (public URLs or local files). It explicitly distinguishes this tool from instagram_approve, so an agent can place it in the workflow 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?

It states the key usage condition — run this before instagram_approve because "Nothing is posted until instagram_approve" — and implies the scheduling case via publish_at. It stops short of explicit exclusions (e.g., don't call it to check status of an already-approved publish, use instagram_get_publish_status instead), so it is clear context rather than a complete decision rule.

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