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

No annotations are provided, so the description carries the full behavioral burden, and it only states what is fetched and by what key. It doesn't say whether the underlying ref can expire, what happens on an invalid/unknown ref, whether access is scoped, or that the operation is non-mutating beyond the implication of 'Retrieve'.

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?

A single front-loaded sentence with no filler - the action and the key input are both in the first clause. It is efficient, though so terse that it leaves behavioral gaps that other dimensions must penalize.

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 explained, and the one required parameter is identified. What is missing is error/expiry behavior and any tie-in to the compression tool that generates the refs, leaving the agent to infer failure modes.

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 100% and the single parameter 'ref' is already documented in the schema as 'CCR ref from a compressed message (ref=ccr_...)'. The description's 'via CCR ref' adds no format, sourcing, or validity detail beyond that, 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?

States a specific verb (Retrieve) and resource (the original content for a compressed block) plus the mechanism (via CCR ref), so an agent can separate it from context_compress, context_prepare and context_normalize. It does not explicitly name a sibling, which keeps it short of a 5.

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 use case is implied by the phrase 'for a compressed block' - you come here when you hold a ref produced by compression. There is no explicit when-to-use statement, no named alternative, and no exclusions (e.g. what to do if the ref is stale or expired).

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