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

Annotations already declare readOnly, idempotent, non-destructive; the description adds meaningful behavioral context beyond annotations: precise payment conditions, free re-reads, auth requirements, and equivalent HTTP route. It also explains the billing occurs only once per checkpoint version.

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?

The purpose and alternative are front-loaded, but the billing information is repeated redundantly: '$0.002 ONLY when...' appears twice in slightly different form, causing unnecessary length and a run-on feel.

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?

Covers purpose, alternative, cost/free conditions, not-found behavior, authentication, and HTTP route. Although there is no output schema, 'verbatim what was stored' adequately describes the return shape for this simple fetch tool.

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 input schema already explains both scope and agent_key with examples and usage guidance. The description's mention of agent_key as a header fallback adds little beyond the schema, so a baseline 3 is appropriate.

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 the last checkpoint verbatim — what was stored, with no briefing composed around it.' It also explicitly contrasts with resume_packet, making its distinct role clear.

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 tells when to use something else: 'Most callers want resume_packet instead, which folds in what arrived while you were gone...' It also covers the not-found case and billing behavior, so the agent knows exactly when this tool is appropriate.

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