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

readOnlyHint=true already tells the agent this is a safe read, and the description adds useful context that reports are signed and retained only 90 days. It omits what happens on an expired or unknown digest (error vs empty), which matters for a digest-keyed lookup.

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?

One sentence, front-loaded with the action and keyed resource, with the retention constraint appended. Nothing is padded.

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?

For a single-param read tool with annotations covering safety, the description covers what is fetched and the retention window. The only real gap is expected failure behavior for expired/missing digests, which is minor here.

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 0% and the single param is just typed string, so the description carries the burden; saying 'sha256 digest' tells the agent the expected format, which the schema does not. It could still clarify encoding (hex) and length.

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 ('Fetch a stored signed report') plus the lookup key ('by its sha256 digest'), so an agent knows exactly what it does. It does not differentiate from the sibling coldread_verify_report, which is a real ambiguity given both operate on signed reports.

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?

Usage is implied: call this when you already hold a digest. The 90-day retention note hints at a precondition, but there is no explicit guidance on when to use this versus coldread_verify_report or coldread_check.

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