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

Annotations only declare safety/idempotency flags, so the description's added context is valuable: credit cost varies by platform and post count, and longer runs return a job_id to be polled via xcut_get_job. That async behavior is exactly the kind of trait annotations cannot express. It does not, however, say when the sync path ends and the job path begins (no threshold), leaving a practical unknown.

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 sentences, front-loaded with the trigger condition, then cost/async behavior, then the exclusion. Every sentence carries distinct information and nothing is repeated from the schema.

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 partially compensates by naming the metric fields returned and disclosing the job_id handoff for long runs. What remains unstated is pagination/volume limits on the returned table and the exact credit formula, but the essentials for correct invocation are present.

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%, so every parameter is already documented, including the days-vs-posts choice and the default of 20 posts. The description restates the same notion ('last N posts or days') without adding syntax or exclusivity rules beyond the schema, so the 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 names a specific verb+resource — per-post metrics (views, likes, comments, shares, engagement) for an account's last N posts or days — and enumerates the supported platforms. It also explicitly separates itself from the nearest sibling by naming xcut_find_outliers, so an agent can route 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?

It states the triggering intent ('when the user wants... for a performance review or to compare accounts') and gives an explicit exclusion with the alternative tool ('Do not use to find standout posts (use xcut_find_outliers)'). Both the use case and the negative case are covered.

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