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

With no annotations, the description carries the full burden and does well: it discloses that this is an interactive UI invocation, that the composer performs the actual creation, and that the host must support apps or the workflow falls back to create_post. It does not cover auth requirements, what the call returns (e.g., whether the created post is returned), or how long the composer session lives.

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 first sentence is a long enumeration but it is front-loaded with the core action and the 'composer creates the post itself' clarification. The subsequent usage sentences all earn their place; only the long per-platform list is arguably more detail than an agent needs.

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 zero-required-param UI-opening tool with no output schema and no annotations, the description covers the important behaviors: host requirement, prefill expectation, and the do-not-double-create rule. It leaves the return value of the call unspecified, which is the main remaining gap.

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 already 86% and the schema documents title, mediaType, mediaUrls, accountIds, and scheduled_at clearly. The description restates some of this and adds per-platform option names (YouTube visibility, TikTok privacy/duet/stitch, Pinterest board, etc.) that are not actual parameters, which risks confusing the agent about what can be passed. Baseline 3 is appropriate.

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 (open the interactive post composer) and immediately clarifies the crucial distinction that the composer, not this tool directly, creates the post. It is unmistakably separable from the sibling create_post, list_posts, and update_post.

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 gives explicit when-to-use ('whenever the user wants to create or schedule a post and the host can show apps'), a prefill instruction, an explicit when-not ('do NOT call create_post yourself after it opens'), and names the alternative path (call create_post in hosts without app support). This is a complete routing rule.

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