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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds meaningful behavior beyond that: the signature is validated against a keyring anchored on a pinned root fingerprint, and it enumerates the returned fields. It omits failure behavior (e.g., what happens on signature mismatch).

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 compact sentences, front-loaded with what the checkpoint is, followed by trust anchoring and the verification alternative. Every sentence carries information; no filler.

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?

There is no output schema, but the description compensates by naming the return fields (tree_size, root_sha256, timestamp, signer, signature_valid). For a zero-parameter read-only tool with full annotation coverage, 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?

The tool takes no parameters, so there is nothing for the description to disambiguate; the baseline for a zero-parameter tool applies. No misleading or missing parameter information.

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 resource ('latest signed tree head of the LEGION MCP transparency log') and what is done with it (signature checked against keyring, anchored on pinned root fingerprint). It is readily distinguishable from the verify_*/check_* siblings, which perform verification rather than retrieval.

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?

It gives clear context for when this is useful (obtaining a checkpoint for trustless verification) and explicitly routes the agent to `how_to_verify_yourself` for that follow-up. It does not, however, state when-not to use it or contrast against the verify_*/check_* siblings.

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