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

Annotations already establish it is a non-read-only, non-idempotent, open-world mutation. The description adds genuine behavioral context beyond that: the two-phase upload handshake, the one-time client token, and the required second call to register the blob. It omits auth/permission requirements and error behavior, but the flow disclosure is meaningful.

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 information-dense sentences, front-loaded with the core action and then the mode-specific instructions. The trailing 'Related:' list is lightly useful for discovery but is the least load-bearing part.

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?

An output schema exists, so return values need not be described, and annotations cover the safety profile for this mutation. The description fully covers both invocation modes and the multi-step upload flow, leaving only minor gaps around permissions and failure handling.

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%, so the baseline is 3, but the description adds sequencing semantics the schema cannot: which parameters belong to the URL path versus each stage of the upload path, and that blobUrl/mime/size are supplied on the second (registration) call rather than the first. This is useful workflow context rather than mere repetition.

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+resource ('Adds media to the library') and immediately distinguishes the two operating modes (public URL import vs. file upload). It is clearly separable from siblings like search_assets, get_asset, update_asset, and delete_assets.

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 explicit branching guidance: use source=url for a public https URL, use source=upload for a local file, and call again after the file is in storage. It names related tools but does not state when *not* to use this tool or how it relates to the post-authoring flow (save_post), so it stops short of full routing guidance.

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