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

Annotations already signal mutability (readOnlyHint=false) and idempotency (idempotentHint=true), so the description's burden is reduced. It adds genuinely useful behavior beyond the annotations: 'editing a failed/partial post resets it to draft' and the status-transition rules (draft unschedules; scheduled requires a future scheduledAt and a channel). No contradiction with the annotations — the reset-to-draft behavior is consistent with a mutating, idempotent update.

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 sentences with no fluff; purpose is front-loaded, followed by the editability constraint, the status-transition rule, and a routing cue. Each sentence earns its place. Slightly compressed but well-organized given the tool's high complexity.

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 high-complexity tool (11 params, deeply nested platform-specific objects) with an exhaustive schema and no output schema, the description covers purpose, editability constraints, state transitions, and sibling routing. It doesn't describe the return value, which is acceptable given no output schema exists, and it could mention get_post for retrieval after editing, but the gaps are minor against a very rich schema.

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%, so the baseline is 3 — the schema already documents every parameter in detail (status enum semantics, platform-specific nesting, linkTrackingOverride null behavior). The description adds only a high-level status-transition summary that roughly mirrors the schema's own status description. It correctly doesn't duplicate schema detail, which is appropriate at this parity.

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 ('Update'), a resource ('existing post'), and enumerates what can change (content, schedule, media, labels, status, platform-specific settings). It differentiates from siblings by scoping to existing posts and by naming publish_post as the alternative for immediate publishing — an agent can distinguish this from compose_post/create_post and publish_post without opening schemas.

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 an explicit 'Use this when the user wants to edit an existing post' directive and names publish_post as the alternative for immediate publishing. It also documents the editability constraint (only draft, scheduled, failed, or partial posts). It does not explicitly point to create_post/compose_post for new posts, though the 'existing post' scoping implies the boundary — a small gap.

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