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

Annotations already declare readOnlyHint=true, idempotentHint=true, openWorldHint=false, and destructiveHint=false, so the safety profile is fully covered elsewhere. The description adds a small amount of useful substance by naming the breakdown dimensions (sources, categories, devices), but says nothing about time window, aggregation, or result granularity.

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 compact sentence with no filler. It is front-loaded with the key concept (reader origins) and the three dimensions, though it is terse enough to feel like a label rather than an explanation.

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?

For a simple single-parameter read tool with rich annotations and full schema coverage, the definition is minimally adequate. However, with no output schema, the description should clarify what the sources/categories/devices breakdown actually returns or which time period it covers, and it does not.

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% with a single required post_id parameter whose schema text already points to list_posts. The description adds nothing about the parameter, which is fine given full schema coverage, so the baseline of 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 names the resource (a post's reader origins) and the dimensions returned (sources, categories, devices), but it is a noun phrase with no verb, and the verb comes only from the title. It does not distinguish this from close siblings like get_post_stats, get_post_engagement, or list_traffic_sources, so an agent cannot tell the scope apart without extra inference.

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?

There is no guidance on when to call this tool, no prerequisites, and no mention of alternatives despite several overlapping analytics siblings (get_post_stats, get_post_engagement, list_traffic_sources, get_audience_insights). The agent is left to infer usage entirely from the tool name.

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