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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, covering the safety profile, so the description is not obligated to restate that. However, it adds nothing new: it does not say whether the ID is parsed locally or resolved over the network (relevant given openWorldHint=true) or what happens when the URL is malformed.

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?

A single eight-word sentence with the action front-loaded and no filler. Nothing could be removed without losing 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?

The tool is trivially simple (one param, read-only, output schema present so return values need no explanation), and the description is adequate for that shape. It is still thin on the two things an agent would want: failure behavior on invalid URLs and how this resolver relates to the sibling ID-lookup and post-detail tools.

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 a single parameter at 100% schema description coverage, the schema fully documents 'link', so the baseline of 3 applies. The description contributes no additional meaning such as accepted URL formats or required URL shape.

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 (extract) and resource (Facebook post ID) with the input (post URL) made explicit, so the transformation is unambiguous. It does not differentiate itself from the near-identical siblings facebook_get_page_id, facebook_get_group_id, and instagram_get_post_id, which is the only thing keeping it from a 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?

There is no when-to-use guidance, no statement of what the returned ID is for, and no mention of alternatives such as facebook_get_post_details. The 'from a post URL' clause only weakly implies the precondition, so an agent must infer the routing decision on its own.

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