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

Annotations already establish the safe-read profile (readOnly, idempotent, non-destructive), so the description only needs to add operational context. It does: the default scoping to the active product is a non-obvious behavior an agent must know, and it reiterates the product_id/all_products mutual exclusion. It does not describe pagination or return shape, keeping it from a 5.

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 sentences, front-loaded with the core purpose before the scoping mechanics and use cases. Every sentence contributes, though the closing use-case list is slightly expansive for a simple list tool.

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?

No output schema exists, so the description must at least characterize the result, which it does ('sender identities'), and annotations cover the safety profile. It omits return shape and pagination behavior, the only meaningful gap for a paginated list tool.

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 all four parameters are already documented in the schema. The description restates the product_id/all_products semantics but adds no new format, constraint, or default detail beyond what the schema provides. Baseline 3 is appropriate when the schema carries the load.

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 ('List sender identities') with clear scope ('available in the connected Meisa account'). An agent can immediately distinguish this read tool from write siblings like meisa_create_sender without opening a schema.

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?

Clearly explains when to use each scoping mode ('Use product_id to target one product directly, or all_products=true to fetch senders across every product') and names concrete use cases ('audit, setup validation, or finding the right sender_id before creating campaigns and triggers'). It lacks explicit when-not guidance or a named alternative sibling, so it stops short of 5.

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