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

Annotations already declare this a safe, idempotent, closed-world read, so the description's job is to add payload behavior — and it does: aggregated story rollup, status breakdown, distinct sprint set, and the fact that stories come back as slim stubs with a named field set. It does not say what happens with an unknown epicId or whether story stubs are truncated, which keeps it out of the top score.

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?

Two sentences, zero filler. Purpose and return contents come first, the pivot guidance comes second, and every clause carries new information (rollup metrics, stub field list, next-step tools).

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?

With no output schema, the description must carry the return contract, and it does so comprehensively — aggregate shape plus stub field list. Minor gaps remain around failure behavior for a bad id and whether the story stub list is bounded, but nothing essential to a correct call 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?

There is a single parameter at 100% schema description coverage ('UUID of the epic'), so the schema fully carries parameter meaning. The description adds only the phrase 'by id', which restates rather than extends the schema — 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?

The description opens with a specific verb and resource ('Get an epic by id') and immediately enumerates what the response contains: rollup counts, points, status breakdown, and distinct sprints. That detail distinguishes it cleanly from list_epics (enumeration) and get_story (single story), so an agent can select it without opening the 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?

Usage is implied rather than stated: fetching one epic by its id. The only explicit routing advice points downstream ('pivot to specific stories with get_story or update_story'), not at how to choose this tool over siblings like list_epics or get_story_context. It never says when not to use it or where the epicId comes from.

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