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

Annotations already declare a safe read (readOnlyHint=true, destructiveHint=false, openWorldHint=false), and the description adds substantial behavior beyond that: cross-workspace default scope, newest-first ordering, per-item workspace labeling, and the paging limit imposed when workspaceId is omitted. It also discloses a cross-tool constraint (mediaIds are only usable for accounts in the same workspace), which is exactly the kind of non-obvious behavior an agent would otherwise get wrong.

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 compact sentences, front-loaded with what is listed and followed by parameter defaults, scope behavior, and downstream usage. Every clause carries operational information; there is no filler or restatement of the title.

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?

With no output schema and zero schema description coverage, the description does well to describe return contents (per-item workspace label, reusable mediaIds) and ordering. The main residual gap is how limit/offset interact with the stated 100-item paging constraint, which the agent must infer.

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 0%, so the description must carry the burden and it does for the two semantically loaded parameters: the VIDEO default and IMAGE enum choice, plus workspaceId's narrowing and paging role. limit and offset are only indirectly implied by 'page past the newest 100 items' and are otherwise left to the schema's numeric bounds.

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?

States a specific verb and resource ('List active media in your media libraries') and scoped qualifier ('active'), which cleanly separates it from list_posts, list_accounts, list_workspaces, and get_carousel among the siblings. An agent can identify the correct tool without opening the 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 concrete invocation guidance: mediaType defaults to VIDEO and IMAGE should be used for JPEGs, and workspaceId narrows scope and is required to page past the newest 100 items. It also routes the agent forward by naming publish_post and schedule_post as consumers of the returned mediaIds, though it never explicitly says when to prefer a different listing sibling.

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