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

Beyond the annotations, the description discloses key behavioral traits: partial-update semantics ('Only the fields you pass are changed'), side effects on budget and invoicing, and immediate propagation ('both take effect immediately, with no separate recalculation step'). This substantially exceeds what annotations alone convey and matches the non-read, non-destructive 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?

The description is three tight sentences: it states the action, clarifies partial-update behavior, and then details the two consequential side effects. Every sentence adds operational value with no filler.

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 mutation with 10 optional parameters and no output schema, the description covers the behavior that matters most: partial updates and immediate financial/invoicing consequences. It does not describe return values or validation edge cases, but the existing content is sufficient for correct invocation in most cases.

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?

With 0% schema description coverage, the description must compensate, and it does add meaning for total_cost, markup_percentage, and is_billable. However, it uses 'markup' instead of the actual parameter name markup_percentage and does not address the remaining seven optional fields, leaving some burden on the schema property names.

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 starts with a specific verb and resource: 'Update a material line.' This clearly identifies the operation and target. It does not explicitly distinguish itself from sibling create/get/delete material tools, though the verb and object make the intent reasonably unambiguous.

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 no guidance on when to use this tool instead of projects_create_material, projects_delete_material, or projects_get_materials. It implies usage through the verb 'Update' but does not state conditions, prerequisites, or exclusions.

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