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

Annotations already convey read-only, idempotent, and non-destructive behavior. The description adds context that it supports date ranges and returns metrics for various source types, but does not disclose additional behaviors like pagination, rate limits, or platform-specific nuances. This is consistent with annotations and adds some value, but not significantly beyond them.

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?

The description is two sentences, front-loaded with 'Fetches analytics', and every word earns its place. It is efficient and easy to scan.

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?

Given that annotations cover safety and an output schema exists to document return values, the description is adequately complete. It covers the core purpose, source types, and date range support. It does not mention optional parameters or platform variations, but these are handled in the schema, so no significant gaps remain.

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%, so the baseline is 3. The description provides examples of source types ('social account, page, profile, location, or channel') that loosely map to platform and channel_id, but these are already elaborated in the schema's parameter descriptions. The description does not add substantive meaning beyond what the schema already provides.

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 clearly states a specific verb ('Fetches') and resource ('analytics for a connected Postly source'), and it distinguishes from sibling tools like postly_get_post_analytics by specifying 'social account, page, profile, location, or channel' rather than a post. It also implies a contrast with postly_list_analytics_sources by returning metrics rather than listing sources.

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?

The description provides clear context about the intended input (a connected Postly source) and mentions date range filtering, which helps an agent understand when to use it. However, it does not explicitly state exclusions or alternatives (e.g., 'for post-level analytics, use postly_get_post_analytics'), so it stops short of fully explicit guidance.

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