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

Annotations already declare readOnly/idempotent/openWorld, but the description adds value beyond them: no authentication required, the privacy boundary (does not expose the private archive original), and the failure semantics when the ID is unmapped or integrity validation fails. That is meaningful behavioral context an agent cannot get from structured fields.

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 tight sentences, front-loaded with the operation and scope, then returns, then error handling. No filler or restated boilerplate.

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?

Even without an output schema, the description enumerates what comes back (mapped packet, source IDs, canonical URL, integrity information) and covers auth and failure modes. Nothing an agent needs to call this 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?

Schema coverage is 100% for the single story_id parameter, so the schema already documents length bounds and the 'private archive IDs are not accepted' constraint. The description only adds the provenance hint that the ID is copied from search results, which the schema largely covers; 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 ('Read one public What Happened packet by story_id') and pins the scope with 'public' versus the private archive original. It names the sibling tool that produces the ID, so an agent can distinguish it from search_public_story_records without opening either schema.

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 routes the agent: the story_id is 'normally copied from search_public_story_records', and it prescribes failure behavior ('use the returned status and do not substitute a guessed ID'). Precondition and error path are both covered rather than left to inference.

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