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

Annotations already cover read-only and open-world safety. The description adds genuinely useful behavior the annotations do not: the metadata comes from a best-effort HEAD request, content-type and size may be approximate, and it never returns bytes.

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 tight sentences, each earning its place: what is fetched, what is returned, and when to use it. The most decision-relevant constraint ('never the bytes') is front-loaded.

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 spelled out, yet the description still clarifies the key output distinction (URL, not bytes). With annotations covering safety and the schema covering inputs, nothing an agent needs to call it correctly is missing.

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 both parameters are already documented. The description restates them ('the owning repo (handle or DID) and the blob CID') without adding format or syntax beyond the schema, making this baseline-level contribution.

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 ('Get metadata for a single blob') and immediately scopes what is returned ('the URL, never the bytes'). The word 'single' cleanly distinguishes it from the sibling list_blobs.

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?

Explicitly says when to use it: 'to turn a blob ref (CID) found in a record into a downloadable link and learn what it is.' It gives clear context but never names a sibling alternative or an exclusion, so it stops short of the top tier.

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