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

Annotations already declare readOnly/idempotent/openWorld/non-destructive, so the safety profile is covered. The description adds real behavioral context beyond that: the env-var vs arg precedence (sitemap_url overrides POSTS_SITEMAP_URL), the configured Ghost API fallback, and the returned metadata fields.

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 paragraphs: discovery modes first, then return/filter shape, then the when-to-use routing. Every sentence carries information an agent needs, with no restatement of the name or title.

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 an output schema present, the description needn't enumerate return values, yet it does so briefly without harm. Safety and discovery configuration are well covered; the only gap is the limit parameter's role in result truncation and any pagination behavior.

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 coverage is already 80%, so the baseline is 3, but the description adds precedence rules not present in the schema chain ('sitemap_url arg overrides POSTS_SITEMAP_URL env var', 'required if neither env var is set') and clarifies urls[] as a full bypass. The limit parameter is still unexplained, but the added meaning is genuine.

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 names a specific verb and resource (discover/list posts) and enumerates the three discovery mechanisms plus the explicit urls[] bypass, which no sibling offers. It also distinguishes itself from the snapshot/verdict/cohort tools by framing itself as the eligibility-discovery step that feeds them.

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?

It gives a clear 'When to use' line tying the tool to snapshot/verdict/cohort analysis and explains the alternative path (pass urls[] to skip discovery). It stops short of stating when NOT to use it or how it differs operationally from posts_snapshot, but the routing context is unambiguous.

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