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

readOnlyHint=true already declares this a safe read, so the description's job is to add context — and it does: it discloses the exact field set returned and explains that specRevision is the revision needed to edit the spec, an implicit concurrency hint for a subsequent write. It does not describe failure behavior when neither key nor featureID is supplied, which is the remaining gap.

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 dense but well-structured sentence that is front-loaded with the core action and then enumerates return fields in priority order. No filler, though the inline parenthetical aliases (workAssigneeID, attaches, ord) make the single sentence heavier than ideal.

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 carries full responsibility for return values and discharges it thoroughly. The only unaddressed case is that both parameters are optional with no stated default or error behavior when neither is provided.

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 both parameters are self-documenting ('not with featureID' / 'not with key'), so the schema already carries the semantics. The description repeats the #F12 key convention but adds no new parameter guidance, making the baseline 3 correct.

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 ('Returns a feature by ID or key') and then enumerates the exact payload: spec, gist, plan tasks ordered by ord, bugs, employees, designs/attachments with file IDs, and specRevision. This level of return-content detail makes it distinguishable from siblings like feature_list or feature_search even though those names are not cited.

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?

Gives an explicit trigger condition ('Useful when the user asks about a feature, its plan or who works on it'), which tells the agent when this is the right call. It stops short of naming an alternative (feature_list vs feature_search vs feature_context) or stating exclusions, so it does not reach a 5.

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