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

Annotations already cover safety (readOnlyHint) and scope (openWorldHint), so the bar is lower. The description still adds real value by disclosing the 404-on-missing-record behavior and that the records are 'stored public' data, which is not derivable from annotations.

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?

Two tight clauses with zero filler; the primary fetch behavior and identifier are front-loaded before the sibling routing guidance. Every sentence earns its place.

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?

A read-only single-record fetch with full annotation coverage, a fully described single parameter, and an output schema. The 404 behavior and sibling routes are the only extras an agent needs, and both 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?

Only one parameter with 100% schema description coverage, so the schema already documents `page_id`. The description restates 'by `page_id`' without adding format, sourcing, or validation detail, 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?

States a specific verb (Fetch) and resource (one stored public Facebook Page contact record) keyed by `page_id`, and explicitly names the two sibling tools it is not. An agent can distinguish this from search/facets without opening any 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?

Explicitly routes the agent: use datasets_facebook_pages_search to find Pages and datasets_facebook_pages_facets for distributions, implying this tool is for when a `page_id` is already known. Strong alternative-naming, though it stops short of a direct 'do not call without an id' exclusion.

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