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

Annotations already cover readOnly, idempotent, non-destructive and closed-world, so the description's added value is the auth constraint (admin-scoped token for org variables) and the failure mode (not-found raises an error rather than returning empty), plus the explicit return shape. That is real context beyond the annotations, though encryption/masking of the value is not discussed.

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 tight sentences: action first, scope rules second, failure and return shape last. No filler, and the most decision-relevant information (scoping) is front-loaded.

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 five-parameter read tool with no output schema, it covers action, scope resolution, auth requirement, error behaviour and the returned fields – everything needed to call it correctly and interpret the result.

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; the description exceeds it by stating how parameters combine – which fields form each scope and that org replaces owner. The schema itself only says "omit when passing org" on the owner field, so the combination rules are genuine added meaning.

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?

"Read one Actions variable by name" gives a specific verb (read) and a single, bounded resource, and the phrase "one ... by name" implicitly separates it from merjax_list_variables and merjax_set_variable. No sibling is named explicitly, so it stops short of the top mark.

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?

It spells out the exact scope combinations that select each variant: owner+repo for repository scope, owner+repo+environment for environment scope, org alone for organisation scope. It also flags the admin-scoped token prerequisite for the org path and that a missing variable is an error, though it never says when to prefer merjax_list_variables instead.

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