describe_blob

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

With no annotations, the description carries the full burden and does so well: it declares read-only behavior, that bytes are never returned, and enumerates the stores consulted (artifact_files, code_snippets, bundles.code_hash). It lacks auth/permission or rate-limit context, so not a full 5.

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?

Front-loaded with the verb and resource, and every sentence is informative (scope, stores, output fields, cross-reference). It restates the return fields that the output schema already covers, which is slight redundancy but not bloat.

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?

Given an output schema exists, the description need not explain return values, yet it usefully clarifies resolved_in semantics (multiple stores may hold a hash). For a single-parameter lookup tool the definition is fully sufficient to call it 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 schema already specifies the "sha256:<64 hex>" format for content_hash. The description adds only "by digest" and the notion of a digest living in multiple stores, which is marginal over the structured field.

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 ("Describe a content-addressed blob by digest") plus scope (read-only, metadata only). It explicitly contrasts with the sibling get_blob, so an agent can distinguish the two 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?

Names the concrete use case ("the read upstream servers use to verify a digest before accepting it on a registration call") and routes to the alternative for bytes ("For the bytes themselves, get_blob"). When-to-use and the alternative are both explicit.

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