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

Beyond the readOnlyHint=true and openWorldHint=true annotations, the description discloses rich behavior: live resolution from the official API with the account's own token, URL expiry of a few hours, and platform-specific fetch constraints (TikTok needs session cookies for a browser-like fetch). These details materially affect how an agent should consume the result and are not present in the annotations. No contradiction with annotations.

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 sentences with zero waste: core purpose front-loaded, followed by two dense platform-specific caveats that are essential for correct usage. Every sentence earns its place, and the Instagram/TikTok split is cleanly structured.

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 tool whose schema fully documents that parameter, the description covers the behavioral complexities (expiry, token, cookies) and implies the response shape (a URL, plus cookies in the TikTok case). The only gap is the absence of an exact response schema, but an agent still has enough to call and interpret the tool correctly.

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% and the post_id property is already fully described ('Post id (UUID, the id field from list_my_account_posts)'). The description reinforces that the post belongs to the org's own My Accounts and adds that the URL is for a video, but it adds little beyond the schema, so 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+resource: 'Get a downloadable URL for the video of one of the org's OWN posts (My Accounts).' It also distinguishes itself from sibling tools like get_post_download_url and get_asset_download_url by explicitly scoping to the org's own My Accounts posts, so an agent can tell them apart 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?

The description gives clear operational context: Instagram URLs resolve live and expire after a few hours (use immediately), while TikTok URLs require returned session cookies and usually cannot be fetched by external services. The '(My Accounts)' qualifier implies the scope boundary versus general-post tools, but no sibling is explicitly named and no when-not-to-use condition is stated.

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