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

Annotations only cover read-only/idempotent/openWorld, so the description carries the real behavioral burden and does: it discloses that values are 'the last stored reading, not a live fetch' with a fetchedAt freshness marker, explains null semantics per platform, and defines supported=false as 'no analytics for the platform, or no post id yet.' That is exactly the kind of staleness and sentinel-value context annotations cannot express.

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?

Dense and front-loaded: shape of the return (summary then per-post detail), then metric list, then edge-case semantics, then the usage call. Slightly long with some enumerations that could be tightened, but every sentence carries information.

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, so the description must describe returns, and it does thoroughly: summary fields, per-platform detail entries, the full metric list, null handling, and freshness. Combined with a single optional parameter, nothing needed to call or interpret this tool 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 description coverage is 100% and the single parameter's schema text already documents the default, the 100 cap, and that the summary always covers every published post. The description restates that the summary is workspace-wide and only detail is limited, adding no syntax or format detail beyond 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?

Opens with a specific verb+resource+scope: 'Metrics for this workspace's published posts,' and immediately names the sibling it is not ('use list_posts for drafts and scheduled posts'). An agent can distinguish this from get_post, list_posts, and check_draft without opening any 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 states the decision context ('Use this to answer whether posts worked') and the boundary condition ('It returns published posts only; use list_posts for drafts and scheduled posts'). Both the when-to-use and the named alternative are present.

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