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

No annotations exist, so the description carries the full burden. It does useful work by disclosing the return shape (reading, trend arrow, staleness in minutes) and the units default chain, but says nothing about what happens with no recent sensor data, data freshness limits, or auth requirements.

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?

Two tight, front-loaded segments: the capability first, then the units contract. Slightly hurt by the dangling quote and the stray leading newline in the units line, but no wasted sentences.

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 single-parameter read tool with no output schema, the description covers payload contents and units adequately. It stops short of describing behavior when the sensor has no recent reading, which is the main failure mode an agent would need to anticipate.

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 0% and the schema only declares an untyped nullable string, so the description must compensate — and it does, giving both allowed values ('mg/dL' or 'mmol/L') and the exact default resolution order (DEXCOM_UNITS, else mg/dL). Only minor gap is that it doesn't say whether an invalid value errors or falls back.

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+resource ('Latest CGM glucose reading') and names the payload ('trend arrow and how old it is'), so the agent knows exactly what comes back. It is clearly narrower than get_glucose and get_glucose_stats via the word 'Latest', but never names those siblings explicitly.

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?

'Latest' and the age-in-minutes output imply the tool is for current-state questions rather than historical ranges, which is usable context. However, there is no explicit when-to-use statement and no routing to get_glucose or get_glucose_stats for history or aggregates.

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

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

With no annotations, the description carries the full burden and does well: it discloses sampling cadence, sort order, default window, and—importantly—that the upstream source silently clips windows beyond 24 hours, a behavior an agent could otherwise get wrong. It stops short of stating auth/permission requirements or what an empty window returns.

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 compact statements, front-loaded with what is returned, followed by per-parameter notes. No filler; every clause conveys a constraint or default the agent needs.

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 parameterless-required read tool with no output schema, the key risks are covered: time window semantics, clipping, cadence, and ordering. It lacks only return-value detail (per-reading fields) and empty-result behavior, which are secondary given no output schema exists to imply shape.

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 0%, so the description must document all three params, and it does: start/end are ISO 8601 with a documented default, units accepts mg/dL or mmol/L. Minor gap: it doesn't say which unit is used when units is null/omitted, leaving the default unresolved.

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 resource and scope: CGM readings in a time window, returned oldest first at ~5-minute cadence. The name plus 'CGM readings' makes the difference from get_current_glucose and get_glucose_stats inferable, but the description never explicitly contrasts itself with those siblings.

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?

Gives useful defaults (last 3 hours) and a hard availability ceiling (Dexcom Share only retains 24 hours, so requests are clipped), which is real usage guidance. However, it never says when to prefer this over get_current_glucose or get_glucose_stats; the agent must infer that from names alone.

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

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

With no annotations, the description carries the full burden and does real work: it discloses the default lookback window and the Share maximum on span, that target thresholds come from DEXCOM_TARGET_LOW/HIGH with 70-180 mg/dL fallbacks, and that percentages are weighted by reading count rather than time. It stops short of stating read-only semantics or behavior on empty/insufficient data, which is reasonable for an obviously read-only aggregation.

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?

Front-loaded with what the tool returns, then short parameter notes in descending order of importance; almost no filler. The line-broken style is terse to the point of being slightly fragmented, but nothing repeats the schema verbatim.

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 and no annotations, so the description must enumerate results — and it does list the full return payload plus defaults and units. Missing pieces are the `units` parameter's effect and edge-case behavior (no data, window exceeding 24h), which keep it from being fully self-contained.

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 0% with five parameters, so the description has to compensate and mostly does: start/end are pinned to ISO 8601 with a stated default and maximum span, and target_low_mg_dl/target_high_mg_dl get units, defaults, and an environment-variable source. The `units` parameter is left completely unexplained, a notable gap given the description insists thresholds are in mg/dL.

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?

It names a specific resource (glucose) and enumerates exactly what is computed: mean, SD, CV, GMI, min/max, and time-in/below/above range. That is far more than a restatement of the name, though it never explicitly distinguishes itself from the siblings get_glucose and get_current_glucose (aggregate vs. raw/instantaneous readings is only implied).

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?

Usage is only implied: the 'last 24 hours, the Share maximum' default and the target-range defaults tell the agent what typical calls look like, but there is no explicit statement of when to choose this over get_glucose or get_current_glucose, and no exclusions or prerequisites.

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