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

Annotations only say readOnly and openWorld; the description adds substantial behavior beyond that: robots.txt is consulted first so closed pages aren't fetched, the fetch is done as mttr rather than X's crawler, results may differ from X's crawler, and the reply includes curl lines to refetch as Twitterbot. It also notes the policy constraint on player cards. This is unusually rich disclosure.

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?

The description is a dense run-on that packs many clauses into long sentences, making the core checks hard to scan. Information is front-loaded reasonably but structure and brevity are poor.

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 single-parameter read-only diagnostic tool, the description covers what is checked and even what the reply contains (curl lines). With no output schema it adequately describes the response, though a clearer list of checks would improve completeness.

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?

With 100% schema coverage on the single url parameter, the schema already documents the parameter. The description adds no format or syntax detail 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 states a specific verb and resource: it tests one live link's X card, enumerating the concrete checks (twitter: tags, robots.txt, player headers). It distinguishes itself from siblings by domain (X card testing) though it never names an alternative tool, so 4 rather than 5.

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 only implied: the url is 'the link to be posted', suggesting a pre-post check. There is no explicit when-to-use/when-not or named alternative among the many mttr_* siblings, so guidance is present but inferred.

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