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

Beyond the annotations (non-read-only, idempotent, non-destructive), the description discloses cost and latency (free but synchronous, server-side render that can take several seconds) and the partial-update contract that omitted fields keep their current values. Those are exactly the traits an agent needs before deciding to call this versus a fast read. No contradiction with the annotation profile.

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?

Purpose and the regenerate alternative come first, then cost/latency, then the batching and image rules, then the account caveat. Every sentence carries information, but the final account-selection sentence is long and slightly tangential to the call itself.

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 do not need explaining. Combined with full annotation coverage and a 100%-documented schema, the description supplies the remaining decision-critical context: eligibility precondition, latency, partial-update semantics, image sourcing, and account disambiguation.

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%, so the baseline would be 3, but the description adds value the schema does not spell out: mediaUrl and uploadId are mutually exclusive alternatives, mediaUrl must be publicly reachable, and the uploadId comes from create_media_upload. The account-selection rule also clarifies what to do with accountId, even though it does not document the field format itself.

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 (re-render a template-designed Pin) plus the three things that can change (overlay title, colors, image). It explicitly distinguishes itself from the sibling that handles AI-generated Pins: regenerate_pin_design.

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?

Gives an explicit precondition (get_pin_design must list "update" in supportedOperations), an explicit alternative for the excluded case (regenerate_pin_design), and an explicit batching rule (send everything in ONE call because each call is a separate render). It also tells the agent to ask the user to pick an account when list_accounts returns more than one.

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