set_custom_format_string

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It adds useful context about the pattern structure (3/4-section, optional [Colour] codes, UNICHAR arrows) and gives an example. However, it does not state potential side effects such as overwriting an existing format, requirements for the measure to exist, or error handling behavior. While the format details are helpful, key behavioral traits remain unspecified.

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 extremely concise: two sentences that lead with the core purpose, provide the key syntactic details, and include a concrete example. No filler or redundancy. Every sentence earns its place, making it easy for an agent to parse quickly.

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?

Despite having no output schema, the description is complete enough for an agent to invoke the tool correctly. It defines the exact format pattern, gives a representative example, and distinguishes from the nearest sibling tool. The absence of output schema is acceptable for a setter tool, and the description covers all necessary input constraints.

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 75% (table, measure, pattern are described, sessionId is not). The description adds significant meaning to the 'pattern' parameter by explaining the 3/4-section structure, optional codes, and providing an example. This goes beyond the schema's simple description. It also implicitly reinforces the 'measure' parameter by using 'measure's'. The uncovered sessionId is not addressed, but overall the description enhances parameter understanding meaningfully.

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 clearly states the tool's purpose: 'Set a measure's STATIC custom format string'. It also specifies the exact resource (measure) and the scope of the operation (format string), and explicitly distinguishes it from the sibling tool set_dynamic_format_string, which is the DAX-driven variant.

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 explicit usage guidance by contrasting with set_dynamic_format_string: 'distinct from set_dynamic_format_string, the DAX-driven one'. This tells the agent when to use this tool (for static format strings) and implicitly when to use the alternative (for DAX-driven formats). The example further clarifies the expected input format.

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