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

Annotations already declare a non-read-only, non-destructive, closed-world write, so the description's extra value is the persistence claim: the mapping applies "for every later send." However, it never says whether an existing mapping is overwritten or merged, nor what happens to fields omitted from the selection.

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?

A single, front-loaded sentence with no filler or repetition. It is efficient, though it is arguably too terse for a tool whose main parameter is an opaque nested object.

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 mutating tool with a nested, entirely undescribed object parameter and no output schema, one sentence leaves out the mapping structure, overwrite semantics, and confirmation of what is returned. An agent could not confidently construct the selection payload from this description alone.

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 0% and the selection parameter is an undocumented free-form object (additionalProperties: true). The description hints that selection holds the fact-to-field pairs, but explains nothing about its shape, nor about connection_id at all.

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?

"Saves which fact goes into which field of a destination" gives a concrete verb (saves) and resource (a fact-to-field mapping on a destination), which is clearer than the bare name. It does not distinguish itself from nearby siblings such as save_your_fields, save_relationships, or update_destination_sync.

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?

There is no statement of when to call this rather than the sibling save/update tools, and no prerequisites (e.g. that a connection and its destination must already exist). The phrase "for every later send" only weakly implies the setup context.

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