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

Annotations already declare readOnly/openWorld/no-destructive, so the safety profile is covered. The description adds value beyond them by disclosing the exact returned fields and the per-request cost ($0.008), which is a meaningful behavioral trait for a billed API. It stops just short of describing rate limits or failure modes.

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 tight sentences, front-loaded with the core action, followed by return values and the chaining/cost notes. Every sentence earns its place with no filler.

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 compensates by enumerating returned fields and the downstream handoff, plus billing cost. For a single-parameter read tool, an agent has everything needed to call it correctly and use the result.

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% for the single 'url' parameter, so the schema documents it fully. The description only restates 'by URL' and adds no format or syntax detail beyond what the schema provides. Baseline 3 is appropriate.

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 ('Get') and resource ('Facebook group') with the input modality ('by URL'). Clearly distinguishes itself from siblings like facebook_group_posts and facebook_page_details by name and resource type.

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?

Provides clear workflow guidance: 'Pass the group ID to facebook_group_posts,' which tells the agent how this tool chains into the next step. It does not state explicit when-not conditions or compare against alternatives like search_facebook_pages, but the context is unambiguous.

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