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

Goes well beyond the readOnly/idempotent annotations by naming the preconditions (needs a generationId) and the exact failure modes (design_not_found, post_already_published for status 'sent'). It also discloses that available operations vary by tier, which is behavioral context an agent cannot infer from annotations or schema.

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?

Front-loads the purpose and the return payload, then layers prerequisites, error cases, and the account-ambiguity rule in a logical order. Slightly overlong because the 'Takes an accountId from list_accounts and a postId from list_posts' sentence duplicates the schema, but every other 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?

For a read tool with full annotations and an output schema, the description covers what an agent still needs: sequencing, tier-dependent operation support, prerequisites, and known error states. Nothing material to a correct first call is missing.

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 100% and the schema already states accountId comes from list_accounts and postId from list_posts, so most of the description's parameter text is redundant. It does add real meaning for accountId by specifying the multi-account disambiguation behavior, which the schema does not express.

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 and resource ('read the design of a Pin') with a precise scope: the AI-generated design, plus the returned fields (tier, variations, sourceImageCandidates, supportedOperations). It is clearly differentiated from siblings like update_pin_design, regenerate_pin_design, get_post, and get_post_image.

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?

Explicit sequencing guidance ('Call this first and follow that list'), an exclusion rationale ('calling one the Pin does not support is rejected'), and a pre-call disambiguation rule for multi-account users ('ask the user which account to use ... do not choose for them'). This is about as actionable as usage guidance gets.

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