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

Annotations already declare readOnly/openWorld=false/idempotent/non-destructive, so the safety profile is covered. The description adds real behavioral context: where the rules come from and what happens when channel is omitted. It stops short of describing the return shape, but an output schema exists for that.

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 short lines, front-loaded with the purpose, then the usage trigger, then the omitted-param rule and related tools. No padding; each sentence carries 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?

An output schema exists, so return values need not be explained. For a simple read-only, single-optional-param tool the description covers purpose, trigger, and default behavior adequately; only a hint about the returned rule structure is absent.

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, and schema coverage is 100% with an enum and an inline description. The description restates the omission behavior already in the schema, adding no format or semantic detail beyond it. Baseline 3 applies when the schema does the work.

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+resource (get format rules for a channel) and enumerates exactly what those rules cover: length limits, hashtags, links, media, tone. Naming the data source ('same source Mark's in-app writer uses') further disambiguates it from generic channel lookups like list_channels.

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 says when to call it ('before writing a post'), what the omitted-parameter behavior is ('list the supported channels'), and routes to related tools (list_channels, save_post, get_brand_context). Both the trigger condition and the alternative path are stated.

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